Add stage 7: email verification magic links and a profile page

Backend
- New Mail namespace: a Mailer interface with SMTP (phpmailer), PHP mail()
  (the default fallback), and log-to-file transports, selected by
  MAIL_TRANSPORT. EmailVerifier issues a hashed, 15-minute magic-link token
  and sends the link (APP_URL/verify-email?token=...).
- Migration 005: email_verifications table + users.verification_email_sent_at.
- Registration now emails a verification link (best effort — a send failure
  doesn't fail registration).
- POST /api/auth/verify-email consumes a token and returns a session, so
  opening the link verifies the address (or applies a pending email change)
  and logs the user in. Single-use; distinct 400s for invalid/used/expired.
- POST /api/email/verification resends; POST /api/email/change requests a
  deferred change (current password required; link goes to the new address;
  users.email only updates when that link is opened). Both throttled to once
  per 60s, returning 429 + retry_after.
- GET /api/me and every session payload now include pending_email. Shared
  SessionPayload builds the user/session JSON for all entry points.

Frontend
- /verify-email view: posts the token, adopts the returned session, redirects.
- /profile view: shows address + status, a resend button with a live cooldown
  (driven by retry_after / 429), and a change-email form (new address +
  current password) that surfaces the pending change.
- Header shows a "verify email" badge linking to the profile.

Tests: 9 new (EmailVerificationTest) covering the link lifecycle, throttle,
and deferred change; AuthTest folded into ApiTestCase, which now routes mail
to a per-test log. Suite: 32 passing.

Co-Authored-By: Claude Sonnet 5 <noreply@anthropic.com>

web/src/App.vue

@@ -1,5 +1,5 @@
 <script setup lang="ts">
-import { RouterView, useRouter } from 'vue-router'
+import { RouterLink, RouterView, useRouter } from 'vue-router'
 import { useAuthStore } from './stores/auth'
 import { useItemsStore } from './stores/items'
 import { useListsStore } from './stores/lists'
@@ -23,8 +23,10 @@ async function onLogout() {
       <span class="app__brand">Todo List</span>
 
       <div v-if="auth.isAuthenticated" class="app__account">
-        <span class="app__email">{{ auth.user?.email }}</span>
-        <span v-if="!auth.emailVerified" class="badge badge--warn">email unverified</span>
+        <RouterLink v-if="!auth.emailVerified" to="/profile" class="badge badge--warn">
+          verify email
+        </RouterLink>
+        <RouterLink to="/profile" class="app__email">{{ auth.user?.email }}</RouterLink>
         <button type="button" class="link" @click="onLogout">Log out</button>
       </div>
     </header>