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.

.gitignore

@@ -92,6 +92,10 @@ cmd/benchmark/data
 !strfry.conf
 !config.toml
 !.dockerignore
+!*.jsx
+!*.tsx
+!/dist
+!bun.lock
 # ...even if they are in subdirectories
 !*/
 /blocklist.json