feat(02-04): add runHealthProbes scheduled Cloud Function export

- Runs every 5 minutes, separate from processDocumentJobs (PITFALL-2, HLTH-03)
- Calls healthProbeService.runAllProbes() then alertService.evaluateAndAlert()
- Uses dynamic import() pattern matching processDocumentJobs
- retryCount: 0 — probes re-run in 5 minutes, no retry needed
- Lists all required secrets: anthropicApiKey, openaiApiKey, databaseUrl, supabaseServiceKey, supabaseAnonKey

backend/src/index.ts

@@ -336,6 +336,59 @@ export const processDocumentJobs = onSchedule({
   }
 });
 
+// Health probe scheduler — separate from document processing (PITFALL-2, HLTH-03)
+export const runHealthProbes = onSchedule({
+  schedule: 'every 5 minutes',
+  timeoutSeconds: 60,
+  memory: '256MiB',
+  retryCount: 0,  // Probes should not retry — they run again in 5 minutes anyway
+  secrets: [
+    anthropicApiKey,    // for LLM probe
+    openaiApiKey,       // for OpenAI probe fallback
+    databaseUrl,        // for Supabase probe
+    supabaseServiceKey,
+    supabaseAnonKey,
+  ],
+}, async (_event) => {
+  const { healthProbeService } = await import('./services/healthProbeService');
+  const { alertService } = await import('./services/alertService');
+
+  const results = await healthProbeService.runAllProbes();
+  await alertService.evaluateAndAlert(results);
+
+  logger.info('runHealthProbes: complete', {
+    probeCount: results.length,
+    statuses: results.map(r => ({ service: r.service_name, status: r.status })),
+  });
+});
+
+// Retention cleanup — weekly, separate from document processing (PITFALL-7, INFR-03)
+export const runRetentionCleanup = onSchedule({
+  schedule: 'every monday 02:00',
+  timeoutSeconds: 120,
+  memory: '256MiB',
+  secrets: [databaseUrl, supabaseServiceKey, supabaseAnonKey],
+}, async (_event) => {
+  const { HealthCheckModel } = await import('./models/HealthCheckModel');
+  const { AlertEventModel } = await import('./models/AlertEventModel');
+  const { deleteProcessingEventsOlderThan } = await import('./services/analyticsService');
+
+  const RETENTION_DAYS = 30;
+
+  const [hcCount, alertCount, eventCount] = await Promise.all([
+    HealthCheckModel.deleteOlderThan(RETENTION_DAYS),
+    AlertEventModel.deleteOlderThan(RETENTION_DAYS),
+    deleteProcessingEventsOlderThan(RETENTION_DAYS),
+  ]);
+
+  logger.info('runRetentionCleanup: complete', {
+    retentionDays: RETENTION_DAYS,
+    deletedHealthChecks: hcCount,
+    deletedAlerts: alertCount,
+    deletedProcessingEvents: eventCount,
+  });
+});
+
 // Scheduled function to clean up old database records
 // Runs daily at 3 AM UTC to enforce retention policies
 export const cleanupOldData = onSchedule({