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/pages/OpsPipeline.tsx

@@ -1,5 +1,5 @@
 import { useState, useEffect } from 'react';
-import { usePipelineHealth, useRetryFailedExtractions } from '../api/hooks';
+import { usePipelineHealth, useRetryFailedExtractions, usePipelineToggle } from '../api/hooks';
 import { LoadingSpinner, DateRangeSelector, Card } from '../components/ui';
 
 const QUEUE_LABELS: Record<string, string> = {
@@ -54,12 +54,14 @@ export function OpsPipelinePage() {
   const { data, isLoading } = usePipelineHealth(hours);
   const stream = usePipelineStream();
   const retryMutation = useRetryFailedExtractions();
+  const toggleMutation = usePipelineToggle();
 
   if (isLoading) return <LoadingSpinner />;
 
   const parsing = (data?.parsing ?? {}) as Record<string, unknown>;
   const extraction = (data?.extraction ?? {}) as Record<string, unknown>;
   const aggregation = (data?.aggregation ?? {}) as Record<string, unknown>;
+  const pipelineEnabled = (data?.pipeline_enabled ?? true) as boolean;
 
   // Prefer live stream data for queue depths and doc stages, fall back to initial fetch
   const queueDepths = stream?.queue_depths
@@ -82,6 +84,14 @@ export function OpsPipelinePage() {
       <div className="flex items-center justify-between">
         <h1 className="text-xl font-semibold text-gray-100">Pipeline Health</h1>
         <div className="flex items-center gap-3">
+          <button
+            type="button"
+            onClick={() => toggleMutation.mutate(!pipelineEnabled)}
+            disabled={toggleMutation.isPending}
+            className={`rounded-md px-3 py-1.5 text-xs font-medium text-white ${pipelineEnabled ? 'bg-green-600 hover:bg-green-500' : 'bg-red-600 hover:bg-red-500'} disabled:opacity-50`}
+          >
+            {toggleMutation.isPending ? '…' : pipelineEnabled ? 'Pipeline ON' : 'Pipeline OFF'}
+          </button>
           {failedCount > 0 && (
             <button
               type="button"