fix(SEC-REVIEW-4-7): Address remaining MEDIUM security review findings

- Graceful container shutdown: detect "not running" containers and skip
  force-remove escalation, only SIGKILL for genuine stop failures
- data: URI stripping: add security audit logging via NestJS Logger
  when data: URIs are blocked in markdown links and images
- Orchestrator bootstrap: replace void bootstrap() with .catch() handler
  for clear startup failure logging and clean process.exit(1)

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

apps/orchestrator/src/main.ts

@@ -17,4 +17,7 @@ async function bootstrap() {
   logger.log(`🚀 Orchestrator running on http://${host}:${String(port)}`);
 }
 
-void bootstrap();
+bootstrap().catch((err: unknown) => {
+  logger.error("Failed to start orchestrator", err instanceof Error ? err.stack : String(err));
+  process.exit(1);
+});