Add bill action pipeline, admin health panel, and LLM provider fixes

- Fetch bill actions from Congress.gov and populate the action timeline
- Add nightly batch task and beat schedule for active bill actions
- Add admin reprocess endpoint for per-bill debugging
- Add BriefPanel with "What Changed" view and version history
- Add External API Health section with per-source latency testing
- Redesign Manual Controls as health panel with status dots and descriptions
- Add Resume Analysis task for stalled LLM jobs
- Add Backfill Dates & Links task for bills with null metadata
- Fix LLM provider/model DB overrides being ignored (env vars used instead)
- Fix Gemini 404: gemini-1.5-pro deprecated → gemini-2.0-flash
- Fix Anthropic models list: use REST API directly (SDK too old for .models)
- Replace test-LLM full analysis with lightweight ping (max_tokens=20)
- Add has_document field to BillDetail; show "No bill text published" state
- Fix "Introduced: —" showing for bills with null introduced_date
- Add bills_missing_sponsor and bills_missing_metadata to admin stats
- Add GovInfo health check using /collections endpoint (fixes 500 from /packages)

Authored-By: Jack Levy

backend/app/workers/celery_app.py

@@ -15,6 +15,7 @@ celery_app = Celery(
         "app.workers.news_fetcher",
         "app.workers.trend_scorer",
         "app.workers.member_interest",
+        "app.workers.notification_dispatcher",
     ],
 )
 
@@ -37,6 +38,7 @@ celery_app.conf.update(
         "app.workers.news_fetcher.*": {"queue": "news"},
         "app.workers.trend_scorer.*": {"queue": "news"},
         "app.workers.member_interest.*": {"queue": "news"},
+        "app.workers.notification_dispatcher.*": {"queue": "polling"},
     },
     task_queues=[
         Queue("polling"),
@@ -72,5 +74,9 @@ celery_app.conf.update(
             "task": "app.workers.congress_poller.fetch_actions_for_active_bills",
             "schedule": crontab(hour=4, minute=0),  # 4 AM UTC, after trend + member scoring
         },
+        "dispatch-notifications": {
+            "task": "app.workers.notification_dispatcher.dispatch_notifications",
+            "schedule": crontab(minute="*/5"),  # Every 5 minutes
+        },
     },
 )