feat: add hApp management endpoints for listing, installing, and removing happs using the installed edge node container

[SIR-R0B]

Summary
Adds Node Manager support for installing and managing multiple always-on hApps from the management UI.

Changes:

• Add a UI section for pasting hApp configuration JSON.
• Install hApps through the EdgeNode container using install_happ.
• Persist submitted hApp configs and installed-app records.
• Display installed hApps in Node Manager.
• Add a Remove action using uninstall_happ.
• Add authenticated API routes:
  -> GET /manage/apps
  -> POST /manage/apps/install
  -> POST /manage/apps/remove
• Include installed hApps in /manage/status.
• Validate app names and required configuration fields.
• Preserve an existing config if a replacement installation fails.
• Restrict permissions on persisted hApp configuration data.
• Document the new routes and storage paths.

Validation

• VS Code diagnostics pass.
• git diff --check passes.
• Full cargo check could not be run because Cargo is unavailable in the development container.