Migrate all components and pages to shadcn/ui with DataTable

Replace custom markup across all pages and components with shadcn/ui
primitives (Dialog, Sheet, Select, Card, Tabs, etc.). Add reusable
DataTable component powered by @tanstack/react-table with sortable
column headers and client-side pagination. Introduce TransactionList
with responsive mobile cards and desktop DataTable, dashboard section
customization (DashboardSection, SectionConfigDialog), and settings
API types.

Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>

frontend/src/components/SectionConfigDialog.tsx

@@ -0,0 +1,137 @@
+import { useState } from 'react';
+import type { SectionSettings } from '../api';
+import { Button } from '@/components/ui/button';
+import { Input } from '@/components/ui/input';
+import { Label } from '@/components/ui/label';
+import {
+  Dialog,
+  DialogContent,
+  DialogHeader,
+  DialogTitle,
+  DialogFooter,
+} from '@/components/ui/dialog';
+import {
+  Select,
+  SelectContent,
+  SelectItem,
+  SelectTrigger,
+  SelectValue,
+} from '@/components/ui/select';
+import { COLOR_OPTIONS, getColorClasses } from '@/lib/colors';
+import { cn } from '@/lib/utils';
+
+interface Props {
+  sectionId: string;
+  settings: SectionSettings;
+  open: boolean;
+  onOpenChange: (open: boolean) => void;
+  onSave: (sectionId: string, updated: Partial<SectionSettings>) => void;
+}
+
+function ColorSwatch({ color }: { color: string }) {
+  const classes = getColorClasses(color);
+  return (
+    <span className="flex items-center gap-2">
+      <span className={cn('w-3 h-3 rounded-full', classes.bg, classes.ring, 'ring-1')} />
+      {color}
+    </span>
+  );
+}
+
+export default function SectionConfigDialog({ sectionId, settings, open, onOpenChange, onSave }: Props) {
+  const [label, setLabel] = useState(settings.label);
+  const [color, setColor] = useState(settings.color);
+  const [cardColor, setCardColor] = useState(settings.cardColor);
+  const [visible, setVisible] = useState(settings.visible);
+  const [order, setOrder] = useState(String(settings.order));
+
+  const handleSave = () => {
+    onSave(sectionId, {
+      label,
+      color,
+      cardColor,
+      visible,
+      order: parseInt(order) || 0,
+    });
+    onOpenChange(false);
+  };
+
+  return (
+    <Dialog open={open} onOpenChange={onOpenChange}>
+      <DialogContent className="sm:max-w-md">
+        <DialogHeader>
+          <DialogTitle>Configure Section</DialogTitle>
+        </DialogHeader>
+
+        <div className="space-y-4">
+          <div className="space-y-2">
+            <Label>Label</Label>
+            <Input value={label} onChange={(e) => setLabel(e.target.value)} />
+          </div>
+
+          <div className="space-y-2">
+            <Label>Section Color</Label>
+            <Select value={color} onValueChange={setColor}>
+              <SelectTrigger className="w-full">
+                <SelectValue />
+              </SelectTrigger>
+              <SelectContent>
+                {COLOR_OPTIONS.map((c) => (
+                  <SelectItem key={c} value={c}>
+                    <ColorSwatch color={c} />
+                  </SelectItem>
+                ))}
+              </SelectContent>
+            </Select>
+          </div>
+
+          <div className="space-y-2">
+            <Label>Card Color</Label>
+            <Select value={cardColor} onValueChange={setCardColor}>
+              <SelectTrigger className="w-full">
+                <SelectValue />
+              </SelectTrigger>
+              <SelectContent>
+                {COLOR_OPTIONS.map((c) => (
+                  <SelectItem key={c} value={c}>
+                    <ColorSwatch color={c} />
+                  </SelectItem>
+                ))}
+              </SelectContent>
+            </Select>
+          </div>
+
+          <div className="flex items-center gap-3">
+            <Label htmlFor={`visible-${sectionId}`}>Visible</Label>
+            <input
+              id={`visible-${sectionId}`}
+              type="checkbox"
+              checked={visible}
+              onChange={(e) => setVisible(e.target.checked)}
+              className="h-4 w-4 rounded border-input accent-primary cursor-pointer"
+            />
+          </div>
+
+          <div className="space-y-2">
+            <Label>Order</Label>
+            <Input
+              type="number"
+              min="0"
+              max="10"
+              value={order}
+              onChange={(e) => setOrder(e.target.value)}
+              className="w-20"
+            />
+          </div>
+        </div>
+
+        <DialogFooter>
+          <Button variant="outline" onClick={() => onOpenChange(false)}>
+            Cancel
+          </Button>
+          <Button onClick={handleSave}>Save</Button>
+        </DialogFooter>
+      </DialogContent>
+    </Dialog>
+  );
+}