Modernize email: Gmail OAuth2 sending, configured under Settings

Retire env-var SMTP basic-auth and send the contact form through Gmail over
OAuth2 (SMTP XOAUTH2), configured in Admin -> Settings -> Email via an in-app
"Connect Gmail" consent flow. Reuses the existing google SSO OAuth client; the
captured refresh token is stored AES-GCM-encrypted (write-only over the API,
never returned), mirroring the auth-provider and Discord-bot secret patterns.

- schema: new email_config singleton table (mirrors bot_config)
- model: emailConfig.{db,model} with encrypted refresh token + getSafe/getWithSecret
- mailer: nodemailer OAuth2 transport (client id/secret from the google provider
  row), contact recipient = contact_email setting, mailto: fallback preserved,
  plus sendTest()
- routes/controller: /admin/email config, connect start+callback (ssoState CSRF
  + PKCE), test, disconnect
- client: EmailDelivery section on the Settings page + api methods; Settings copy
  now spells out that contact_email is the delivery recipient
- docs/env: drop SMTP_*/CONTACT_TO from env examples; update README/BACKEND_DESIGN
- tests: emailConfig.model + mailer suites (8 new; full suite 142 pass)

Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_01XKeCQEJZr1AFJN4Bgcmvh3

README.md

@@ -39,7 +39,7 @@ The design reference is [BACKEND_DESIGN.md](BACKEND_DESIGN.md) (API contract, sc
 | Auth | Session service over JWT: httpOnly cookie (web) + bearer access/refresh tokens (mobile), bcrypt hashing, optional TOTP 2FA (`speakeasy` + `qrcode`), pluggable OAuth2/OIDC SSO (built-in Google & Discord + generic) |
 | Database | MariaDB 11 (own container) |
 | Frontend | React 18, Vite 5, React Router 6 |
-| Email | Nodemailer (SMTP) with a `mailto:` fallback |
+| Email | Nodemailer via Gmail OAuth2 (configured in admin), with a `mailto:` fallback |
 | API docs | OpenAPI 3.0 via `swagger-autogen`, served with `swagger-ui-express` at `/api/docs` |
 | Deploy | Docker Compose, Pangolin reverse proxy |
 
@@ -276,8 +276,7 @@ Copy `.env.example` (Compose) or `server/.env.example` (local) and fill in. **`.
 | `TOTP_ISSUER` | `UOMysticmoon` | label shown in authenticator apps for optional per-user 2FA |
 | `TOTP_CHALLENGE_TTL` | `5m` | lifetime of the short-lived post-password "awaiting code" step |
 | `ADMIN_USERNAME` / `ADMIN_PASSWORD` | — | first-admin bootstrap (first boot only) |
-| `SMTP_HOST` / `SMTP_PORT` / `SMTP_USER` / `SMTP_PASS` | — | optional; blank → contact form uses `mailto:` |
-| `CONTACT_TO` | `UOMysticmoon@gmail.com` | contact recipient |
+| _Email_ | — | configured in Admin → Settings → Email (Gmail OAuth2), not via env; recipient = `contact_email` setting |
 | `CLIENT_ORIGIN` | `http://localhost:5173` | enables CORS in dev only |
 | `LOG_LEVEL` / `FILE_LOG_LEVEL` | `info` / `debug` | console / file verbosity |
 | `LOG_TO_FILE` / `LOG_DIR` / `LOG_FILE` | `true` / `<server>/logs` / `app.log` | log file (bind-mounted to `./logs` in Docker) |
@@ -343,8 +342,9 @@ Copy `.env.example` (Compose) or `server/.env.example` (local) and fill in. **`.
 
 - `helmet`, admin routes `noindex` + `robots.txt` disallow, `trust proxy` for correct client IPs
   behind Pangolin (see `TRUST_PROXY`), first admin seeded from env (no hardcoded credentials),
-  `.env` git-ignored. Passwords and request bodies are never logged. SMTP is optional — the contact
-  form falls back to a `mailto:` link when unconfigured.
+  `.env` git-ignored. Passwords and request bodies are never logged. Email sends through Gmail
+  OAuth2 configured in the admin (refresh token stored AES-GCM-encrypted, never in env); the
+  contact form falls back to a `mailto:` link when unconfigured.
 
 ---