feat: add reports center, admin drill-down, disease filter + bug fixes + perf optimization

Frontend features:
- 报表中心 (ReportsCenter): list/detail views, diagnosis breakdown chart, CSV export
- 多级行政下钻 (AdminBreadcrumb): 湖北省→武汉市→区→街道 hierarchical drill-down
- 按病种筛选 (DiseaseFilter): multi-select diagnosis filter on monitoring + reports pages

Backend:
- Add /forecast/{days} endpoint, diagnosis filter params on cases endpoints
- Add /streets aggregation endpoint, enrich reports with real case data
- Extract shared case_loader module

Bug fixes (14):
- Fix missing /risk/forecast route (404), historyApi pointing to non-existent router
- Fix min_risk filter silently ignored in insights/hotspots
- Fix type mismatches: CaseTrendResponse, CaseStatsResponse shapes
- Fix silent .catch(() => {}) swallowing errors, fetchAlerts not clearing stale state
- Fix lru_cache caching exceptions, generateReport used cachedGet for write op
- Fix missing useEffect deps in Insights, DistrictComparison, ReportsCenter

Performance (9):
- Zustand selectors across 9 components (eliminate re-render cascades)
- Fix districtCases.sort() mutating store state, inline IIFE → memo'd component
- CaseLocationMap: React.memo, race protection, correct deps
- AlertCard: stable callbacks, TimelinePlayer: useMemo, TopNav: clock isolation
- SideNav: modules array to module scope, DiseaseFilter: memoized filter

frontend/src/components/SideNav.tsx

@@ -6,6 +6,48 @@ interface SideNavProps {
   alertCount?: number;
 }
 
+const modules: { id: string; label: string; icon: React.ReactNode; items: { id: string; label: string }[] }[] = [
+  {
+    id: 'monitoring',
+    label: '监测',
+    icon: (
+      <svg className="w-4 h-4" fill="currentColor" viewBox="0 0 24 24">
+        <path d="M3 13h8V3H3v10zm0 8h8v-6H3v6zm10 0h8V11h-8v10zm0-18v6h8V3h-8z"/>
+      </svg>
+    ),
+    items: [
+      { id: 'monitoring', label: '监测面板' },
+    ],
+  },
+  {
+    id: 'alert',
+    label: '预警',
+    icon: (
+      <svg className="w-4 h-4" fill="currentColor" viewBox="0 0 24 24">
+        <path d="M12 22c1.1 0 2-.9 2-2h-4c0 1.1.89 2 2 2zm6-6v-5c0-3.07-1.64-5.64-4.5-6.32V4c0-.83-.67-1.5-1.5-1.5s-1.5.67-1.5 1.5v.68C7.63 5.36 6 7.92 6 11v5l-2 2v1h16v-1l-2-2z"/>
+      </svg>
+    ),
+    items: [
+      { id: 'alerts', label: '预警地图' },
+    ],
+  },
+  {
+    id: 'analysis',
+    label: '分析',
+    icon: (
+      <svg className="w-4 h-4" fill="currentColor" viewBox="0 0 24 24">
+        <path d="M19 3H5c-1.1 0-2 .9-2 2v14c0 1.1.9 2 2 2h14c1.1 0 2-.9 2-2V5c0-1.1-.9-2-2-2zM9 17H7v-7h2v7zm4 0h-2V7h2v10zm4 0h-2v-4h2v4z"/>
+      </svg>
+    ),
+    items: [
+      { id: 'trend-analysis', label: '趋势分析' },
+      { id: 'district-comparison', label: '区域对比' },
+      { id: 'insights', label: '智能洞察' },
+      { id: 'reports', label: '报表中心' },
+    ],
+  },
+];
+
 export function SideNav({
   activePage,
   onPageChange,
@@ -13,47 +55,6 @@ export function SideNav({
 }: SideNavProps) {
   const [expanded, setExpanded] = useState<string | null>('monitoring');
 
-  const modules: { id: string; label: string; icon: React.ReactNode; items: { id: string; label: string }[] }[] = [
-    {
-      id: 'monitoring',
-      label: '监测',
-      icon: (
-        <svg className="w-4 h-4" fill="currentColor" viewBox="0 0 24 24">
-          <path d="M3 13h8V3H3v10zm0 8h8v-6H3v6zm10 0h8V11h-8v10zm0-18v6h8V3h-8z"/>
-        </svg>
-      ),
-      items: [
-        { id: 'monitoring', label: '监测面板' },
-      ],
-    },
-    {
-      id: 'alert',
-      label: '预警',
-      icon: (
-        <svg className="w-4 h-4" fill="currentColor" viewBox="0 0 24 24">
-          <path d="M12 22c1.1 0 2-.9 2-2h-4c0 1.1.89 2 2 2zm6-6v-5c0-3.07-1.64-5.64-4.5-6.32V4c0-.83-.67-1.5-1.5-1.5s-1.5.67-1.5 1.5v.68C7.63 5.36 6 7.92 6 11v5l-2 2v1h16v-1l-2-2z"/>
-        </svg>
-      ),
-      items: [
-        { id: 'alerts', label: '预警地图' },
-      ],
-    },
-    {
-      id: 'analysis',
-      label: '分析',
-      icon: (
-        <svg className="w-4 h-4" fill="currentColor" viewBox="0 0 24 24">
-          <path d="M19 3H5c-1.1 0-2 .9-2 2v14c0 1.1.9 2 2 2h14c1.1 0 2-.9 2-2V5c0-1.1-.9-2-2-2zM9 17H7v-7h2v7zm4 0h-2V7h2v10zm4 0h-2v-4h2v4z"/>
-        </svg>
-      ),
-      items: [
-        { id: 'trend-analysis', label: '趋势分析' },
-        { id: 'district-comparison', label: '区域对比' },
-        { id: 'insights', label: '智能洞察' },
-      ],
-    },
-  ];
-
   const handleItemClick = (moduleId: string, itemId: string) => {
     setExpanded(moduleId);
     onPageChange(itemId);