fix: infrastructure hardening and documentation improvements

- Add *.sqlite* patterns to .gitignore
- Expand .dockerignore to exclude chart/, docs/, .github/, etc.
- Add HEALTHCHECK instruction to Dockerfile
- Fix Helm chart: preserve JWT secret across upgrades (lookup),
  add securityContext, conditional PVC creation, resource defaults
- Remove hardcoded demo credentials from MCP.md
- Complete .env.example with all configurable environment variables

https://claude.ai/code/session_01SoQKcF5Rz9Y8Nzo4PzkxY8

.gitignore

@@ -11,6 +11,9 @@ client/public/icons/*.png
 *.db
 *.db-shm
 *.db-wal
+*.sqlite
+*.sqlite-shm
+*.sqlite-wal
 
 # User data
 server/data/