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

chart/values.yaml

@@ -38,7 +38,13 @@ persistence:
   uploads:
     size: 1Gi
 
-resources: {}
+resources:
+  requests:
+    cpu: 100m
+    memory: 256Mi
+  limits:
+    cpu: 500m
+    memory: 512Mi
 
 ingress:
   enabled: false