feat(mui): SidebarNav — MUI List nav with white-pill active state

Add src/admin/ui/SidebarNav.tsx: drawer content component using MUI
List/ListItemButton with NavLink polymorphism. Active item uses the
`selected` prop for the white "pill" styling (not NavLink active class).
Renders logo header, permission-filtered nav sections, and user/logout
footer. Not yet wired — next task mounts it in a Drawer.

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

src/admin/ui/SidebarNav.tsx

@@ -0,0 +1,172 @@
+import { NavLink, useLocation } from "react-router-dom";
+import Box from "@mui/material/Box";
+import List from "@mui/material/List";
+import ListItemButton from "@mui/material/ListItemButton";
+import ListItemIcon from "@mui/material/ListItemIcon";
+import ListItemText from "@mui/material/ListItemText";
+import Typography from "@mui/material/Typography";
+import Avatar from "@mui/material/Avatar";
+import Button from "@mui/material/Button";
+import { useAuth } from "../context/AuthContext";
+import { useTheme as useAppTheme } from "../../context/ThemeContext";
+import { menuSections, isItemActive, hasItemPermission } from "./navData";
+
+interface SidebarNavProps {
+  /** Closes the mobile drawer on item click (optional — desktop omits it). */
+  onNavigate?: () => void;
+  /** Logout handler, owned by the parent. */
+  onLogout: () => void;
+}
+
+export default function SidebarNav({ onNavigate, onLogout }: SidebarNavProps) {
+  const { user, hasPermission } = useAuth();
+  const { theme } = useAppTheme();
+  const location = useLocation();
+
+  const visibleSections = menuSections
+    .map((section) => ({
+      ...section,
+      items: section.items.filter((item) =>
+        hasItemPermission(item, hasPermission),
+      ),
+    }))
+    .filter((section) => section.items.length > 0);
+
+  return (
+    <Box
+      sx={{ display: "flex", flexDirection: "column", height: "100%", p: 1.5 }}
+    >
+      {/* Logo header */}
+      <Box sx={{ px: 1, py: 1 }}>
+        <Box
+          component="img"
+          src={`/api/admin/company-settings/logo?variant=${theme === "dark" ? "dark" : "light"}`}
+          alt="Logo"
+          onError={(e) => {
+            e.currentTarget.src =
+              theme === "dark"
+                ? "/images/logo-dark.png"
+                : "/images/logo-light.png";
+          }}
+          sx={{
+            maxHeight: 40,
+            maxWidth: "100%",
+            objectFit: "contain",
+            display: "block",
+          }}
+        />
+      </Box>
+
+      {/* Nav */}
+      <Box sx={{ flex: 1, overflowY: "auto", mt: 1 }}>
+        {visibleSections.map((section) => (
+          <Box key={section.label}>
+            <Typography
+              variant="caption"
+              sx={{
+                display: "block",
+                px: 1.5,
+                py: 0.5,
+                textTransform: "uppercase",
+                letterSpacing: ".06em",
+                fontWeight: 700,
+                color: "text.secondary",
+                fontSize: ".64rem",
+              }}
+            >
+              {section.label}
+            </Typography>
+            <List disablePadding>
+              {section.items.map((item) => (
+                <ListItemButton
+                  key={item.path}
+                  component={NavLink}
+                  to={item.path}
+                  end={item.end}
+                  onClick={onNavigate}
+                  selected={isItemActive(item, location.pathname)}
+                  sx={{
+                    borderRadius: 2,
+                    mb: 0.25,
+                    py: 0.6,
+                    color: "text.secondary",
+                    "& svg": { width: 18, height: 18 },
+                    "&.Mui-selected, &.Mui-selected:hover": {
+                      bgcolor: "background.paper",
+                      color: "primary.main",
+                      fontWeight: 700,
+                      boxShadow: "0 2px 8px rgba(20,20,40,0.07)",
+                    },
+                  }}
+                >
+                  <ListItemIcon sx={{ minWidth: 32, color: "inherit" }}>
+                    {item.icon}
+                  </ListItemIcon>
+                  <ListItemText
+                    primary={item.label}
+                    primaryTypographyProps={{
+                      fontSize: ".82rem",
+                      fontWeight: "inherit",
+                    }}
+                  />
+                </ListItemButton>
+              ))}
+            </List>
+          </Box>
+        ))}
+      </Box>
+
+      {/* Footer */}
+      <Box sx={{ pt: 1, mt: 1, borderTop: 1, borderColor: "divider" }}>
+        <Box
+          sx={{ display: "flex", alignItems: "center", gap: 1, px: 0.5, mb: 1 }}
+        >
+          <Avatar
+            sx={{
+              width: 34,
+              height: 34,
+              bgcolor: "primary.main",
+              fontSize: ".8rem",
+              fontWeight: 700,
+              fontFamily: "'Urbanist', sans-serif",
+            }}
+          >
+            {user?.fullName?.charAt(0) || user?.username?.charAt(0) || "U"}
+          </Avatar>
+          <Box sx={{ minWidth: 0 }}>
+            <Typography noWrap sx={{ fontSize: ".82rem", fontWeight: 600 }}>
+              {user?.fullName || user?.username}
+            </Typography>
+            <Typography
+              noWrap
+              sx={{ fontSize: ".7rem", color: "text.secondary" }}
+            >
+              {user?.roleDisplay}
+            </Typography>
+          </Box>
+        </Box>
+        <Button
+          fullWidth
+          color="inherit"
+          onClick={onLogout}
+          startIcon={
+            <svg
+              viewBox="0 0 24 24"
+              width="18"
+              height="18"
+              fill="none"
+              stroke="currentColor"
+              strokeWidth="2"
+            >
+              <path d="M9 21H5a2 2 0 0 1-2-2V5a2 2 0 0 1 2-2h4" />
+              <polyline points="16 17 21 12 16 7" />
+              <line x1="21" y1="12" x2="9" y2="12" />
+            </svg>
+          }
+        >
+          Odhlásit se
+        </Button>
+      </Box>
+    </Box>
+  );
+}