fix(ui): cross-module mechanical unifications (line-item labels/align, back-tab targets, status-button colors, apply_vat checkbox, currency-from-settings, read-only issued_by, Celkem header, centered offer tabs)

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

src/admin/pages/OfferDetail.tsx

@@ -335,7 +335,7 @@ function SortableItemRow({
             InputProps={{ readOnly }}
           />
           <TextField
-            label="Cena/ks"
+            label="Jedn. cena"
             type="number"
             value={item.unit_price}
             onChange={(e) => onUpdate("unit_price", parseFloat(e.target.value))}
@@ -1167,14 +1167,25 @@ export default function OfferDetail() {
               <Button
                 onClick={() => setInvalidateConfirm(true)}
                 variant="outlined"
-                color="inherit"
+                color="error"
               >
                 Zneplatnit
               </Button>
             )}
             {!readOnly && (
               <Button onClick={handleSave} disabled={saving}>
-                {saving ? "Ukládání..." : "Uložit"}
+                {saving ? (
+                  <>
+                    <CircularProgress
+                      size={16}
+                      color="inherit"
+                      sx={{ mr: 1 }}
+                    />
+                    Ukládání...
+                  </>
+                ) : (
+                  "Uložit"
+                )}
               </Button>
             )}
             {canDelete && hasPermission("offers.delete") && (
@@ -1513,16 +1524,20 @@ export default function OfferDetail() {
                         #
                       </TableCell>
                       <TableCell>Popis</TableCell>
-                      <TableCell sx={{ width: "5rem" }}>Množství</TableCell>
+                      <TableCell sx={{ width: "5.5rem" }} align="center">
+                        Množství
+                      </TableCell>
                       <TableCell sx={{ width: "5rem" }}>Jednotka</TableCell>
-                      <TableCell sx={{ width: "8rem" }}>Cena/ks</TableCell>
+                      <TableCell sx={{ width: "8rem" }} align="center">
+                        Jedn. cena
+                      </TableCell>
                       <TableCell sx={{ width: "4rem" }} align="center">
                         V ceně
                       </TableCell>
                       <TableCell sx={{ width: "8rem" }} align="right">
                         Celkem
                       </TableCell>
-                      {!readOnly && <TableCell sx={{ width: "3rem" }} />}
+                      {!readOnly && <TableCell sx={{ width: "2.5rem" }} />}
                     </TableRow>
                   </TableHead>
                   <TableBody>