Unify address selection UI (#801)

* feat: unify address selection UI

* docs: update changelog for address UI

* feat: restore user mailbox tab

AGENTS.md

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+# Repository Guidelines
+
+## Project Structure
+- Backend: `worker/` (Workers API; entry `worker/src/worker.ts`, APIs under `worker/src/*_api/`).
+- Frontend: `frontend/` (Vue 3 app; routes in `frontend/src/router/`).
+- Pages middleware: `pages/functions/_middleware.js`.
+- Mail parser: `mail-parser-wasm/` (Rust WASM).
+- SMTP/IMAP proxy: `smtp_proxy_server/`.
+- DB schema/migrations: `db/`.
+- Docs: `vitepress-docs/`.
+
+## Build & Dev Commands
+Run inside each folder:
+- Frontend: `pnpm dev`, `pnpm build`.
+- Worker: `pnpm dev`, `pnpm lint`, `pnpm build`.
+- Pages: `pnpm dev`.
+- Docs: `pnpm dev` in `vitepress-docs/`.
+- WASM: `wasm-pack build --release` in `mail-parser-wasm/`.
+- SMTP proxy: `pip install -r smtp_proxy_server/requirements.txt` then `python smtp_proxy_server/main.py`.
+
+## Coding Style
+- Follow existing module style. `worker/` uses TypeScript + ESLint; `frontend/` uses Vue SFCs.
+- Keep current naming patterns: `*_api/`, `utils/`, `models/`.
+- ESM imports only (`type: module`).
+
+## Testing
+- No formal test runner. Validate with local dev servers and key flows (login, inbox, send/receive).
+
+## Commits & PRs
+- Use Conventional Commits (`feat:`, `fix:`, `docs:`). Recent history includes PR numbers like `(#123)`.
+- PRs should explain scope and add screenshots for UI changes.
+
+## Config Tips
+- Worker settings in `worker/wrangler.toml` (see template for bindings).
+- Frontend uses `VITE_*` env vars. Don’t commit secrets.