feat: add Helm CLI and built-in web file manager

- Install Helm v3.17.1 in Dockerfile for chart development (closes #49)
- Add fileManager toggle using base image's WEB_FILE_MANAGER (closes #11)
- Wire WEB_FILE_MANAGER env vars in deployment template
- Update CLAUDE.md, README.md with new features and values

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via [Happy](https://happy.engineering)

Co-Authored-By: Claude <noreply@anthropic.com>
Co-Authored-By: Happy <yesreply@happy.engineering>

chart/values.yaml

@@ -27,6 +27,16 @@ ide:
 ssh:
   enabled: false
 
+# Web file manager — built-in upload/download via the VNC web interface (port 5800)
+# Uses the base image's WEB_FILE_MANAGER feature (no extra sidecar needed)
+fileManager:
+  enabled: false
+  # Paths the file manager can access (default: AUTO = mapped volumes)
+  # Options: AUTO | ALL | comma-separated list of paths
+  allowedPaths: "/workspace,/config"
+  # Paths to deny (takes precedence over allowedPaths)
+  deniedPaths: ""
+
 # VNC display settings
 display:
   width: "1920"