Embed React app and add new user authentication interface.

- Integrated a React-based web frontend into the Go server using the `embed` package, serving it from `/`.
- Added build and development scripts utilizing Bun for the React app (`package.json`, `README.md`).
- Enhanced auth interface to support better user experience and permissions (`App.jsx`, CSS updates).
- Refactored `/api/auth/login` to serve React UI, removing hardcoded HTML template.
- Implemented `/api/permissions/` with ACL support for user access management.

app/web/.gitignore

@@ -0,0 +1,31 @@
+# Dependencies
+node_modules
+.pnp
+.pnp.js
+
+# Bun
+.bunfig.toml
+bun.lockb
+
+# Build directories
+dist
+build
+
+# Cache and logs
+.cache
+.temp
+.log
+*.log
+
+# Environment variables
+.env
+.env.local
+.env.development.local
+.env.test.local
+.env.production.local
+
+# Editor directories and files
+.idea
+.vscode
+*.swp
+*.swo