feat(offer-detail): mobile card layout for the line-items editor

On phones (< sm) the editable items grid was a wide horizontally-scrolling table of inputs — unusable. SortableItemRow now renders each item as a stacked card (labeled Popis / Množství / Jednotka / Cena/ks inputs, V ceně checkbox + Celkem, drag handle + remove in the header), and the wrapper renders a card stack instead of TableContainer/Table on mobile (DndContext/SortableContext preserved so drag still works via TouchSensor). Desktop keeps the table. Verified: no inner table on mobile, no page horizontal scroll.

Co-Authored-By: Claude Opus 4.8 (1M context) <noreply@anthropic.com>

src/admin/pages/OfferDetail.tsx

@@ -21,6 +21,8 @@ import TableContainer from "@mui/material/TableContainer";
 import TableHead from "@mui/material/TableHead";
 import TableRow from "@mui/material/TableRow";
 import Checkbox from "@mui/material/Checkbox";
+import useMediaQuery from "@mui/material/useMediaQuery";
+import { useTheme } from "@mui/material/styles";
 import {
   offerDetailOptions,
   offerCustomersOptions,
@@ -229,6 +231,8 @@ function SortableItemRow({
     transition,
     isDragging,
   } = useSortable({ id: item._key, disabled: readOnly });
+  const theme = useTheme();
+  const isMobile = useMediaQuery(theme.breakpoints.down("sm"));
   const style = {
     transform: CSS.Transform.toString(transform),
     transition,
@@ -239,6 +243,146 @@ function SortableItemRow({
   };
   const lineTotal =
     (Number(item.quantity) || 0) * (Number(item.unit_price) || 0);
+
+  if (isMobile) {
+    return (
+      <Box
+        ref={setNodeRef}
+        sx={{
+          border: 1,
+          borderColor: "divider",
+          borderRadius: 2,
+          p: 1.5,
+          display: "flex",
+          flexDirection: "column",
+          gap: 1.25,
+          bgcolor: "background.paper",
+          ...style,
+        }}
+      >
+        <Box sx={{ display: "flex", alignItems: "center", gap: 1 }}>
+          {!readOnly && (
+            <IconButton
+              size="small"
+              {...attributes}
+              {...listeners}
+              title="Přetáhnout"
+              aria-label="Přetáhnout"
+              sx={{ cursor: "grab", color: "text.secondary" }}
+            >
+              {DragIcon}
+            </IconButton>
+          )}
+          <Typography
+            variant="caption"
+            sx={{ color: "text.secondary", fontWeight: 700 }}
+          >
+            Položka {index + 1}
+          </Typography>
+          <Box sx={{ flex: 1 }} />
+          {!readOnly && (
+            <IconButton
+              color="error"
+              size="small"
+              onClick={onRemove}
+              title="Odebrat"
+              aria-label="Odebrat"
+              disabled={!canDelete}
+            >
+              {RemoveIcon}
+            </IconButton>
+          )}
+        </Box>
+        <TextField
+          label="Popis"
+          value={item.description}
+          onChange={(e) => onUpdate("description", e.target.value)}
+          placeholder="Název položky"
+          InputProps={{ readOnly }}
+        />
+        <TextField
+          label="Podrobný popis"
+          value={item.item_description}
+          onChange={(e) => onUpdate("item_description", e.target.value)}
+          placeholder="Volitelný"
+          InputProps={{ readOnly }}
+        />
+        <Box
+          sx={{
+            display: "grid",
+            gridTemplateColumns: "repeat(3, minmax(0, 1fr))",
+            gap: 1,
+          }}
+        >
+          <TextField
+            label="Množství"
+            type="number"
+            value={item.quantity}
+            onChange={(e) => onUpdate("quantity", parseInt(e.target.value, 10))}
+            slotProps={{ htmlInput: { step: "1" } }}
+            InputProps={{ readOnly }}
+          />
+          <TextField
+            label="Jednotka"
+            value={item.unit}
+            onChange={(e) => onUpdate("unit", e.target.value)}
+            InputProps={{ readOnly }}
+          />
+          <TextField
+            label="Cena/ks"
+            type="number"
+            value={item.unit_price}
+            onChange={(e) => onUpdate("unit_price", parseFloat(e.target.value))}
+            slotProps={{ htmlInput: { step: "0.01" } }}
+            InputProps={{ readOnly }}
+          />
+        </Box>
+        <Box
+          sx={{
+            display: "flex",
+            alignItems: "center",
+            justifyContent: "space-between",
+          }}
+        >
+          <Box
+            component="label"
+            sx={{
+              display: "flex",
+              alignItems: "center",
+              gap: 0.5,
+              cursor: readOnly ? "default" : "pointer",
+            }}
+          >
+            <Checkbox
+              checked={item.is_included_in_total}
+              onChange={(e) =>
+                onUpdate("is_included_in_total", e.target.checked)
+              }
+              disabled={readOnly}
+            />
+            <Typography variant="body2">V ceně</Typography>
+          </Box>
+          <Box sx={{ textAlign: "right" }}>
+            <Typography
+              variant="caption"
+              sx={{ color: "text.secondary", display: "block" }}
+            >
+              Celkem
+            </Typography>
+            <Typography
+              sx={{
+                fontFamily: "'DM Mono', Menlo, monospace",
+                fontWeight: 600,
+              }}
+            >
+              {formatCurrency(lineTotal, currency)}
+            </Typography>
+          </Box>
+        </Box>
+      </Box>
+    );
+  }
+
   return (
     <TableRow ref={setNodeRef} sx={style}>
       {!readOnly && (
@@ -352,6 +496,8 @@ export default function OfferDetail() {
   const alert = useAlert();
   const { hasPermission } = useAuth();
   const navigate = useNavigate();
+  const theme = useTheme();
+  const isMobile = useMediaQuery(theme.breakpoints.down("sm"));
   const dndSensors = useSensors(
     useSensor(PointerSensor, { activationConstraint: { distance: 5 } }),
     useSensor(TouchSensor, {
@@ -1392,76 +1538,95 @@ export default function OfferDetail() {
           </Typography>
         )}
 
-        <TableContainer sx={{ overflowX: "auto" }}>
-          <DndContext
-            sensors={dndSensors}
-            collisionDetection={closestCenter}
-            modifiers={[restrictToVerticalAxis, restrictToParentElement]}
-            onDragEnd={(event: DragEndEvent) => {
-              const { active, over } = event;
-              if (!over || active.id === over.id) return;
-              setItems((prev) => {
-                const oldIndex = prev.findIndex(
-                  (i) => i._key === String(active.id),
-                );
-                const newIndex = prev.findIndex(
-                  (i) => i._key === String(over.id),
-                );
-                if (oldIndex === -1 || newIndex === -1) return prev;
-                return arrayMove(prev, oldIndex, newIndex);
-              });
-            }}
+        <DndContext
+          sensors={dndSensors}
+          collisionDetection={closestCenter}
+          modifiers={[restrictToVerticalAxis, restrictToParentElement]}
+          onDragEnd={(event: DragEndEvent) => {
+            const { active, over } = event;
+            if (!over || active.id === over.id) return;
+            setItems((prev) => {
+              const oldIndex = prev.findIndex(
+                (i) => i._key === String(active.id),
+              );
+              const newIndex = prev.findIndex(
+                (i) => i._key === String(over.id),
+              );
+              if (oldIndex === -1 || newIndex === -1) return prev;
+              return arrayMove(prev, oldIndex, newIndex);
+            });
+          }}
+        >
+          <SortableContext
+            items={items.map((i) => i._key)}
+            strategy={verticalListSortingStrategy}
           >
-            <SortableContext
-              items={items.map((i) => i._key)}
-              strategy={verticalListSortingStrategy}
-            >
-              <Table
-                size="small"
-                sx={{
-                  minWidth: 720,
-                  "& td, & th": { borderColor: "divider" },
-                }}
-              >
-                <TableHead>
-                  <TableRow>
-                    {!readOnly && <TableCell sx={{ width: "2rem" }} />}
-                    <TableCell sx={{ width: "2.5rem" }} align="center">
-                      #
-                    </TableCell>
-                    <TableCell>Popis</TableCell>
-                    <TableCell sx={{ width: "5rem" }}>Množství</TableCell>
-                    <TableCell sx={{ width: "5rem" }}>Jednotka</TableCell>
-                    <TableCell sx={{ width: "7rem" }}>Cena/ks</TableCell>
-                    <TableCell sx={{ width: "4rem" }} align="center">
-                      V ceně
-                    </TableCell>
-                    <TableCell sx={{ width: "7rem" }} align="right">
-                      Celkem
-                    </TableCell>
-                    {!readOnly && <TableCell sx={{ width: "3rem" }} />}
-                  </TableRow>
-                </TableHead>
-                <TableBody>
-                  {items.map((item, index) => (
-                    <SortableItemRow
-                      key={item._key}
-                      item={item}
-                      index={index}
-                      currency={form.currency}
-                      readOnly={readOnly}
-                      canDelete={items.length > 1}
-                      onUpdate={(field, value) =>
-                        updateItem(index, field as keyof OfferItem, value)
-                      }
-                      onRemove={() => removeItem(index)}
-                    />
-                  ))}
-                </TableBody>
-              </Table>
-            </SortableContext>
-          </DndContext>
-        </TableContainer>
+            {isMobile ? (
+              <Box sx={{ display: "flex", flexDirection: "column", gap: 1.5 }}>
+                {items.map((item, index) => (
+                  <SortableItemRow
+                    key={item._key}
+                    item={item}
+                    index={index}
+                    currency={form.currency}
+                    readOnly={readOnly}
+                    canDelete={items.length > 1}
+                    onUpdate={(field, value) =>
+                      updateItem(index, field as keyof OfferItem, value)
+                    }
+                    onRemove={() => removeItem(index)}
+                  />
+                ))}
+              </Box>
+            ) : (
+              <TableContainer sx={{ overflowX: "auto" }}>
+                <Table
+                  size="small"
+                  sx={{
+                    minWidth: 720,
+                    "& td, & th": { borderColor: "divider" },
+                  }}
+                >
+                  <TableHead>
+                    <TableRow>
+                      {!readOnly && <TableCell sx={{ width: "2rem" }} />}
+                      <TableCell sx={{ width: "2.5rem" }} align="center">
+                        #
+                      </TableCell>
+                      <TableCell>Popis</TableCell>
+                      <TableCell sx={{ width: "5rem" }}>Množství</TableCell>
+                      <TableCell sx={{ width: "5rem" }}>Jednotka</TableCell>
+                      <TableCell sx={{ width: "7rem" }}>Cena/ks</TableCell>
+                      <TableCell sx={{ width: "4rem" }} align="center">
+                        V ceně
+                      </TableCell>
+                      <TableCell sx={{ width: "7rem" }} align="right">
+                        Celkem
+                      </TableCell>
+                      {!readOnly && <TableCell sx={{ width: "3rem" }} />}
+                    </TableRow>
+                  </TableHead>
+                  <TableBody>
+                    {items.map((item, index) => (
+                      <SortableItemRow
+                        key={item._key}
+                        item={item}
+                        index={index}
+                        currency={form.currency}
+                        readOnly={readOnly}
+                        canDelete={items.length > 1}
+                        onUpdate={(field, value) =>
+                          updateItem(index, field as keyof OfferItem, value)
+                        }
+                        onRemove={() => removeItem(index)}
+                      />
+                    ))}
+                  </TableBody>
+                </Table>
+              </TableContainer>
+            )}
+          </SortableContext>
+        </DndContext>
 
         {/* Totals */}
         <Box