Add three-stage cross-domain news research and reading briefings

Group original news into tagged fact packages, review each package with evidence and read-only research, and build complete 72-hour reading lists with independent model selections.

Add paused RSS/Atom subscriptions, news-scoped Skills, versioned analysis records, and locked deployment support for SearXNG. Preserve original news and keep live migration and legacy AI cleanup separately authorized.

Validate with 604 backend tests, 49 frontend tests, 19 CI control tests, lint, type checks, production build, and disposable PostgreSQL migration and three-stage smoke checks.

backend/src/alphapulse/api/settings.py

@@ -154,11 +154,16 @@ async def patch_provider(provider_id: int, body: ProviderPatch, session: Annotat
 @router.delete("/providers/{provider_id}")
 async def delete_provider(provider_id: int, session: Annotated[AsyncSession, Depends(get_session)]) -> ApiResponse[None]:
     provider = await get_provider(session, provider_id)
-    risk = await session.scalar(select(RiskSettings).where(RiskSettings.provider_id == provider_id).with_for_update())
+    risk = await session.scalar(select(RiskSettings).where((RiskSettings.provider_id == provider_id) | (RiskSettings.second_provider_id == provider_id) | (RiskSettings.third_provider_id == provider_id)).with_for_update())
     if risk:
         if risk.enabled:
             raise HTTPException(status.HTTP_409_CONFLICT, "请先暂停新闻 AI 分析或切换其接入配置")
-        risk.provider_id = None
+        if risk.provider_id == provider_id:
+            risk.provider_id = None
+        if risk.third_provider_id == provider_id:
+            risk.third_provider_id = None
+        if risk.second_provider_id == provider_id:
+            risk.second_provider_id = None
     await session.delete(provider)
     await session.flush()
     if provider.is_default: