feat: add inventory statistics section, adapt to latest prototype

- Add GET /api/vehicles/inventory-stats endpoint that groups inventory vehicles by macro-region, city, brand, type, model, and batch
- Add RegionalInventoryStats type and fetchInventoryStats API function
- Add full inventory statistics section with region/model tabs, filters, desktop table, and mobile views
- Add modal filters (plate number, model, brand, location search) to vehicle detail modal
- Update modal header to support title field for contextual naming

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

src/server/routes/vehicles.ts

@@ -813,6 +813,43 @@ app.get('/list', async (c) => {
   );
 });
 
+// GET /api/vehicles/inventory-stats — grouped inventory stats for the inventory statistics section
+app.get('/inventory-stats', async (c) => {
+  const vehicles = await getVehicles();
+  const inventory = vehicles.filter((v) => v.status === 'Inventory');
+
+  const TYPE_NAME_MAP: Record<string, string> = {
+    t4_5: '4.5T普货',
+    t4_5c: '4.5T冷链',
+    t18: '18T',
+    t49: '49T',
+    trailer: '挂车',
+    other: '其他',
+  };
+
+  const groups = new Map<string, number>();
+  for (const v of inventory) {
+    const typeCategory = classifyVehicleType(v);
+    const typeName = TYPE_NAME_MAP[typeCategory];
+    const region = mapMacroRegion(v.province, v.city);
+    const city = v.city || '其他';
+    const brand = v.brandLabel || '未知';
+    const model = v.model;
+    const batch = v.contractNo || 'N/A';
+    const key = `${region}|${city}|${brand}|${typeName}|${model}|${batch}`;
+    groups.set(key, (groups.get(key) || 0) + 1);
+  }
+
+  const result = Array.from(groups.entries())
+    .map(([key, quantity]) => {
+      const [region, city, brand, type, model, batch] = key.split('|');
+      return { region, city, brand, type, model, batch, quantity };
+    })
+    .sort((a, b) => b.quantity - a.quantity);
+
+  return c.json(result);
+});
+
 // GET /api/vehicles/weekly-detail?type=delivered|returned|replaced|pending
 app.get('/weekly-detail', async (c) => {
   const type = c.req.query('type');