Add CRUD web interface via Hummingbird

[leogdion]

Summary

Add web-based CRUD routes to the MistDemo Hummingbird server for CloudKit record operations (create, read, update, delete).

Context

From PR #273 review feedback: the CLI has full CRUD commands (mistdemo create, update, delete, query) but the Hummingbird web server only serves the auth-token flow. The web UI (index.html) needs corresponding REST API routes.

Scope

• Add Hummingbird routes for record CRUD operations (query, create, update, delete)
• Wire routes to existing MistKit service layer
• Update Resources/index.html web UI to consume the new endpoints

🤖 Generated with Claude Code

[leogdion]

Resolved by #333 (commit 62c7b6c).