feat: pipeline on/off toggle with per-stage Helm control

- Added pipelineEnabled flag to Helm values (default: true)
- Worker services (scheduler, ingestion, parser, extractor, aggregation,
  recommendation, broker-adapter, lake-publisher) scale to 0 when disabled
- API services always run regardless of toggle
- Redis-based runtime toggle: POST /api/ops/pipeline/toggle
- Scheduler checks the flag before each cycle
- Frontend: green/red Pipeline ON/OFF button on the pipeline page
- Beta defaults to pipelineEnabled: false
- Base values.yaml: blanked external URLs (Ollama, Polygon, Alpaca)
  so stages only connect to what they explicitly configure

frontend/src/test/mocks/handlers.ts

@@ -106,6 +106,8 @@ export const handlers = [
   http.delete('/api/admin/trading/lockouts/:id', () => HttpResponse.json({ status: 'deleted' })),
   http.get('/api/ops/pipeline/health', () => HttpResponse.json({ hours: 24, document_stages: [{ status: 'extracted', doc_count: 5 }], parsing: {}, extraction: {}, aggregation: {}, queue_depths: {} })),
   http.post('/api/ops/pipeline/retry-failed', () => HttpResponse.json({ retried: 10, message: 'Re-enqueued 10 documents for extraction' })),
+  http.get('/api/ops/pipeline/toggle', () => HttpResponse.json({ pipeline_enabled: true })),
+  http.post('/api/ops/pipeline/toggle', () => HttpResponse.json({ pipeline_enabled: true })),
   http.get('/api/ops/ingestion/summary', () => HttpResponse.json({ total_runs: 10, completed: 8, failed: 2, total_items_fetched: 50, total_items_new: 12, by_source_type: [] })),
   http.get('/api/ops/ingestion/throughput', () => HttpResponse.json([])),
   http.get('/api/ops/model/performance', () => HttpResponse.json({ total_extractions: 20, success_rate: 0.9, avg_duration_ms: 1500, retry_rate: 0.05, avg_confidence: 0.8 })),