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/stores/diseaseStore.ts

@@ -0,0 +1,38 @@
+import { create } from 'zustand';
+import { caseApi } from '@/services/api';
+
+interface DiseaseState {
+  availableDiagnoses: string[];
+  selectedDiagnoses: string[];
+  isLoading: boolean;
+  error: string | null;
+
+  fetchDiagnoses: () => Promise<void>;
+  setSelectedDiagnoses: (diagnoses: string[]) => void;
+  clearDiagnoses: () => void;
+  clearError: () => void;
+}
+
+export const useDiseaseStore = create<DiseaseState>((set, get) => ({
+  availableDiagnoses: [],
+  selectedDiagnoses: [],
+  isLoading: false,
+  error: null,
+
+  clearError: () => set({ error: null }),
+
+  fetchDiagnoses: async () => {
+    const { availableDiagnoses } = get();
+    if (availableDiagnoses.length > 0) return; // already loaded
+    set({ isLoading: true, error: null });
+    try {
+      const data = await caseApi.getDiagnoses();
+      set({ availableDiagnoses: data.diagnoses || [], isLoading: false });
+    } catch (e) {
+      set({ error: (e as Error).message || '加载诊断列表失败', isLoading: false });
+    }
+  },
+
+  setSelectedDiagnoses: (diagnoses) => set({ selectedDiagnoses: diagnoses }),
+  clearDiagnoses: () => set({ selectedDiagnoses: [] }),
+}));