Bundle a Mailpit catcher and default Compose to SMTP

Adds a mailpit service (axllent/mailpit, ~15 MB, in-memory) to
docker-compose.yml — chosen over the unmaintained MailHog for the same
footprint. It has no profile, so `docker compose up -d` starts it alongside
the API; the app defaults to MAIL_TRANSPORT=smtp -> mailpit:1025 (no
auth/TLS) and mail is read at http://localhost:8025.

Also change the default MAIL_FROM to no-reply@todo.test: PHPMailer v7 rejects
the dotless no-reply@localhost as an invalid address.

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

docker-compose.yml

@@ -14,21 +14,30 @@ services:
       JWT_TTL: "${JWT_TTL:-86400}"
       # Magic links point at the frontend dev server.
       APP_URL: "${APP_URL:-http://localhost:5173}"
-      # The container has no MTA, so log emails to a file by default. View them with:
-      #   docker compose exec app cat /var/www/storage/mail.log
-      # Set to "smtp" (with MAIL_SMTP_*) or "mail" to actually send.
-      MAIL_TRANSPORT: "${MAIL_TRANSPORT:-log}"
-      MAIL_FROM: "${MAIL_FROM:-no-reply@localhost}"
-      MAIL_SMTP_HOST: "${MAIL_SMTP_HOST:-}"
-      MAIL_SMTP_PORT: "${MAIL_SMTP_PORT:-587}"
+      # Deliver to the Mailpit catcher below; read mail at http://localhost:8025.
+      MAIL_TRANSPORT: "${MAIL_TRANSPORT:-smtp}"
+      MAIL_FROM: "${MAIL_FROM:-no-reply@todo.test}"
+      MAIL_SMTP_HOST: "${MAIL_SMTP_HOST:-mailpit}"
+      MAIL_SMTP_PORT: "${MAIL_SMTP_PORT:-1025}"
       MAIL_SMTP_USERNAME: "${MAIL_SMTP_USERNAME:-}"
       MAIL_SMTP_PASSWORD: "${MAIL_SMTP_PASSWORD:-}"
-      MAIL_SMTP_ENCRYPTION: "${MAIL_SMTP_ENCRYPTION:-tls}"
+      MAIL_SMTP_ENCRYPTION: "${MAIL_SMTP_ENCRYPTION:-none}"
     volumes:
       # Live source: edit on the host, no image rebuild needed.
       - .:/var/www/html
       # Persistent storage, kept outside /var/www/html to avoid a nested mount.
       - storage:/var/www/storage
+    depends_on:
+      - mailpit
+    restart: unless-stopped
+
+  # Development mail catcher (Mailpit — the maintained MailHog successor). ~15 MB,
+  # single Go binary, messages held in memory. Web UI: http://localhost:8025
+  mailpit:
+    image: axllent/mailpit:v1.31
+    ports:
+      - "8025:8025"   # web UI + REST API
+      - "1025:1025"   # SMTP (also reachable in-network as mailpit:1025)
     restart: unless-stopped
 
   # Optional Vite dev server. Start it with:  docker compose --profile frontend up -d