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/pages/TrendAnalysis.tsx

@@ -32,7 +32,13 @@ const DAY_OPTIONS = [
 ];
 
 export function TrendAnalysis() {
-  const { trendData, isLoading, error, clearError, selectedDays, setSelectedDays, fetchTrend } = useAnalysisStore();
+  const trendData = useAnalysisStore((s) => s.trendData);
+  const isLoading = useAnalysisStore((s) => s.isLoading);
+  const error = useAnalysisStore((s) => s.error);
+  const clearError = useAnalysisStore((s) => s.clearError);
+  const selectedDays = useAnalysisStore((s) => s.selectedDays);
+  const setSelectedDays = useAnalysisStore((s) => s.setSelectedDays);
+  const fetchTrend = useAnalysisStore((s) => s.fetchTrend);
   const [selectedPollutants, setSelectedPollutants] = useState<string[]>(['aqi', 'pm25']);
 
   useEffect(() => {