feat(auth): self-service password reset (backend + web)

Add a full password-reset flow — the prerequisite for the Android app
(docs/android/PLAN.md §8.2), which hands off to the website for reset
rather than shipping a native screen.

Backend:
- password_resets table: stores only the sha256 hash of an opaque 32-byte
  token (mirrors user_invites / mobile_refresh_tokens), single-use, ~1h TTL.
- model/passwordResets + users.getActiveByEmail (email is non-unique, so a
  request can match several accounts, each emailed its own link).
- mailer.sendPasswordReset (fails soft when email is unconfigured).
- Endpoints: POST /auth/password/forgot (always a generic 200 — no account
  enumeration), GET|POST /auth/password/reset/:token. Confirming rotates the
  hash and revokes every session (web cutoff + mobile refresh tokens); it does
  not auto-login, so a 2FA account still passes TOTP next sign-in. Also serves
  SSO-only accounts (null hash) as their set-initial-password path.
- Dedicated request/confirm rate limiters. Swagger regenerated.

Web:
- ForgotPassword + ResetPassword pages, routes /account/forgot and
  /account/reset/:token, and a "Forgot your password?" link on the login page.

Tests: test/passwordResets.test.js (5). All server tests pass; client builds;
end-to-end smoketest against MariaDB passes (no-enumeration, single-use, hash
rotation, session revoke, login with the new password).

Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_01NgyHnrNa8WwG3doxvxjuCr

client/src/api/client.js

@@ -54,6 +54,14 @@ export const api = {
     req(`/auth/invite/${encodeURIComponent(token)}/accept`, { method: 'POST', body: { username, password, ...extra } }),
   loginTotp: (challenge, code) =>
     req('/auth/login/totp', { method: 'POST', body: { challenge, code } }),
+  // Self-service password reset (public, token-gated). forgot always resolves the
+  // same way whether or not the email exists (no enumeration); getPasswordReset
+  // validates a link (200 → { username }, 404 → invalid/expired); resetPassword
+  // sets the new password and revokes all sessions (the user then signs in fresh).
+  forgotPassword: (email) => req('/auth/password/forgot', { method: 'POST', body: { email } }),
+  getPasswordReset: (token) => req(`/auth/password/reset/${encodeURIComponent(token)}`),
+  resetPassword: (token, password) =>
+    req(`/auth/password/reset/${encodeURIComponent(token)}`, { method: 'POST', body: { password } }),
   // Second factor for an SSO login (challenge is held in an httpOnly cookie set by
   // the callback, so only the code is sent). Returns { user, returnTo }.
   ssoLoginTotp: (code) => req('/auth/sso/totp', { method: 'POST', body: { code } }),