SSE Patch 增量推送架构全链路实现

- web/sse_manager.py: asyncio.Queue 连接池 + broadcast + event_stream
- web/routers/sse_router.py: GET /api/events + POST /api/internal/collector-patch
- weather_sources.py: 采集后 POST patch 给 web
- Nginx polyweather.conf: /api/events proxy_buffering off
- frontend/api/events/route.ts: Next.js SSE 代理
- frontend/hooks/use-sse-patches.ts: EventSource + useLatestPatch + 重连
- LiveTemperatureThresholdChart: mergePatchIntoHourly 增量合并
- scan-terminal-query: 接入 SSE patch 更新行数据
- 新增 ssePatchArchitecture.test.ts 架构测试

frontend/components/dashboard/scan-terminal/scan-terminal-client.ts

@@ -18,7 +18,7 @@ export type RemoteData<T> =
   | { status: "error"; error: string; previous?: T };
 
 export const scanTerminalQueryPolicy = {
-  autoRefreshMs: DASHBOARD_REFRESH_POLICY_MS.scanRows,
+  autoRefreshMs: null,
   manualForceRefreshCooldownMs: 2 * 60_000,
 } as const;