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/api/src/knowledge/utils/markdown.ts

@@ -124,6 +124,7 @@ const SANITIZE_OPTIONS: sanitizeHtml.IOptions = {
       const href = attribs.href;
       // Strip data: URI scheme from links
       if (href?.trim().toLowerCase().startsWith("data:")) {
+        logger.warn(`Blocked data: URI in link href`);
         const { href: _removed, ...safeAttribs } = attribs;
         return {
           tagName,
@@ -149,6 +150,7 @@ const SANITIZE_OPTIONS: sanitizeHtml.IOptions = {
     img: (tagName: string, attribs: sanitizeHtml.Attributes) => {
       const src = attribs.src;
       if (src?.trim().toLowerCase().startsWith("data:")) {
+        logger.warn(`Blocked data: URI in image src`);
         const { src: _removed, ...safeAttribs } = attribs;
         return {
           tagName,