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

backend/models.py

@@ -162,6 +162,14 @@ class InsightsResponse(BaseModel):
 # Reports Models
 # ============================================================================
 
+class DiagnosisBreakdown(BaseModel):
+    """Diagnosis breakdown for reports"""
+    diagnosis: str = Field(..., description="Diagnosis name")
+    outpatient: int = Field(..., description="Outpatient count")
+    inpatient: int = Field(..., description="Inpatient count")
+    total: int = Field(..., description="Total cases")
+
+
 class ReportSection(BaseModel):
     """Single section of a report"""
     title: str = Field(..., description="Section title")
@@ -207,6 +215,7 @@ class ReportResponse(BaseModel):
     recommendations: List[ReportRecommendation] = Field(..., description="Recommendations")
     attachments: List[str] = Field(default=[], description="Attachment file paths")
     timestamp: str = Field(..., description="Response timestamp")
+    diagnosis_breakdown: List[DiagnosisBreakdown] = Field(default=[], description="Diagnosis breakdown data")
 
 
 class ReportListResponse(BaseModel):