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>

.env.example

@@ -18,3 +18,23 @@ JWT_SECRET=
 
 # How long an issued token stays valid, in seconds (default: 86400 = 24h).
 JWT_TTL=86400
+
+# Base URL of the frontend. Verification magic links point here, e.g.
+# <APP_URL>/verify-email?token=... (default: http://localhost:5173).
+APP_URL=http://localhost:5173
+
+# Email delivery.
+#   mail  — PHP's built-in mail() function (default)
+#   smtp  — the SMTP server configured below
+#   log   — append messages to MAIL_LOG_PATH instead of sending (dev/test)
+MAIL_TRANSPORT=mail
+MAIL_FROM=no-reply@localhost
+MAIL_FROM_NAME=Todo List
+MAIL_LOG_PATH=storage/mail.log
+
+# Only used when MAIL_TRANSPORT=smtp.
+MAIL_SMTP_HOST=
+MAIL_SMTP_PORT=587
+MAIL_SMTP_USERNAME=
+MAIL_SMTP_PASSWORD=
+MAIL_SMTP_ENCRYPTION=tls          # tls | ssl | none