Add e-mail system: send applications, receive & reply to responses

Send the complete application (body + generated attachments) to a
user-entered address via authenticated SMTP submission through the
account's own server, so it applies DKIM and uses its reputable IP/PTR —
required for deliverability here (domain publishes SPF -all, DMARC
p=reject). From/Return-Path stay aligned on the sending domain.

Reply e-mails are polled over IMAP, parsed, stored and matched to the
right application (via In-Reply-To/References, then sender address);
their attachments are saved and downloadable. The detail page gains a
correspondence thread with compose, threaded reply, and an AI-drafted
reply the user can edit before sending.

New: lib/mailer.js (nodemailer + imapflow + mailparser), generateEmailReply
in lib/documents.js, emails/email_anhaenge/app_state tables, background
poller + manual fetch. Credentials come from MAIL_* env vars (.env, not
committed / not in the image).

Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>

package.json

@@ -13,9 +13,12 @@
   "dependencies": {
     "ejs": "^3.1.9",
     "express": "^4.18.2",
+    "imapflow": "^1.4.3",
     "jspdf": "^2.5.1",
     "jspdf-autotable": "^3.8.2",
+    "mailparser": "^3.9.12",
     "multer": "^2.2.0",
+    "nodemailer": "^9.0.3",
     "sqlite3": "^5.1.6"
   },
   "devDependencies": {