Remove specific account references from public documentation

- Replace FETCHERPAY with generic CUSTOM account examples
- Update README.md, .env.example, and DEPLOY.md with generic configurations
- Remove hardcoded IPs, email addresses, and domain names
- Update package.json description to be more generic

🤖 Generated with [Claude Code](https://claude.com/claude-code)

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

.env.example

@@ -3,15 +3,14 @@
 YAHOO_EMAIL=you@yahoo.com
 YAHOO_APP_PASSWORD=xxxx xxxx xxxx xxxx
 
-# ── FetcherPay self-hosted mail (Dovecot / Poste.io) ─────────────────────────
-# IMAP/SMTP are exposed as Kubernetes NodePorts on the server.
-# Use the direct server IP (not hostname) to avoid K8s internal DNS flakiness.
-FETCHERPAY_EMAIL=you@fetcherpay.com
-FETCHERPAY_PASSWORD=yourpassword
-FETCHERPAY_IMAP_HOST=23.120.207.35   # direct IP avoids EAI_AGAIN; or: mail.fetcherpay.com
-FETCHERPAY_IMAP_PORT=30993           # K8s NodePort — IMAPS (TLS, self-signed cert)
-FETCHERPAY_SMTP_HOST=23.120.207.35
-FETCHERPAY_SMTP_PORT=30587           # K8s NodePort — SMTP + STARTTLS
+# ── Optional: Custom IMAP/SMTP Server ────────────────────────────────────────
+# Uncomment and configure these if you want to use a second email account
+# CUSTOM_EMAIL=you@yourdomain.com
+# CUSTOM_PASSWORD=yourpassword
+# CUSTOM_IMAP_HOST=mail.yourdomain.com
+# CUSTOM_IMAP_PORT=993
+# CUSTOM_SMTP_HOST=mail.yourdomain.com
+# CUSTOM_SMTP_PORT=587
 
 # ── Server ───────────────────────────────────────────────────────────────────
 PORT=3456