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

services/scheduler/app.py

@@ -19,6 +19,7 @@ from services.shared.config import load_config
 from services.shared.db import get_pg_pool, get_redis
 from services.shared.logging import setup_logging
 from services.shared.redis_keys import (
+    PREFIX,
     QUEUE_EXTRACTION,
     QUEUE_INGESTION,
     QUEUE_MACRO_CLASSIFICATION,
@@ -499,12 +500,19 @@ async def main() -> None:
     rds = get_redis(config)
 
     logger.info("Scheduler started (tick=%ds)", SCHEDULER_TICK)
+    pipeline_key = f"{PREFIX}:pipeline:enabled"
     recovery_counter = 0
     retry_counter = 0
     cleanup_counter = 0
     try:
         while True:
             try:
+                # Check pipeline toggle — skip cycle if disabled
+                flag = await rds.get(pipeline_key)
+                if flag == "0":
+                    await asyncio.sleep(SCHEDULER_TICK)
+                    continue
+
                 if await acquire_lock(rds, "scheduler_cycle", ttl=30):
                     try:
                         await schedule_cycle(pool, rds)