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/CaseMap.tsx

@@ -1,7 +1,7 @@
 import { memo, useEffect, useRef, useState, useCallback } from 'react';
 import L from 'leaflet';
 import 'leaflet/dist/leaflet.css';
-import { caseApi } from '@/services/api';
+import { geocodedApi } from '@/services/api';
 import type { CaseGrid, GeocodedCase } from '@/types';
 
 interface CaseMapProps {
@@ -74,8 +74,8 @@ function CaseMapComponent({ height = '480px' }: CaseMapProps) {
       setError(null);
       try {
         const [gridRes, geoRes] = await Promise.all([
-          caseApi.getGrid(),
-          caseApi.getGeocoded(5000),
+          geocodedApi.getGrid(),
+          geocodedApi.getGeocoded({ limit: 5000 }),
         ]);
         if (cancelled) return;
         setGrids(gridRes.grids || []);