Initial build: Asterisk voicemail transcription + portal

- mailcmd replacement (vm_mailcmd.py): faster-whisper transcription (CPU int8),
  extractive summary + intent tags + spoken-digit number extraction,
  multipart/alternative HTML email, fail-safe relay of original message
- Telegram DM delivery (vm_telegram.py) with per-mailbox routing
- Caller-ID -> name (vm_contacts.py): file / google / carddav backends
- SQLite store (vm_store.py) with content-addressed audio
- FastAPI portal (vm_web.py): PIN login, list/play/delete, per-user settings,
  zero JS, loopback-only behind Apache TLS
- Backfill importer (vm_import.py) for existing spool recordings
- systemd unit, Apache vhost + certbot TLS, install.sh
- Docs: INSTALL, CONFIGURATION, ARCHITECTURE, OPERATIONS, SECURITY, TESTING

Verified end-to-end on mail.txt3.net: 157 historical messages backfilled,
live voicemail -> transcribed -> stored -> visible at https://vm.txt3.net.

tests/make_test_mail.py

@@ -0,0 +1,20 @@
+#!/usr/bin/env python3
+"""Build a fake Asterisk voicemail notification (as sendmail -t would get it)."""
+import sys
+from email.message import EmailMessage
+
+wav = sys.argv[1]
+to = sys.argv[2]
+
+m = EmailMessage()
+m["From"] = "voicemail@txt3.net"
+m["To"] = to
+m["Subject"] = "New message 3 in mailbox 1001"
+m.set_content(
+    "Dear Jamie:\n\n\tjust wanted to let you know you were just left a 0:37 long message "
+    "(number 3)\nin mailbox 1001 from Dave Roberts <07941223856>, on Thu, 13 Aug 2026 "
+    "07:12:00, so you might\nwant to check it when you get a chance.  Thanks!\n\n"
+    "\t\t\t\t--Asterisk\n")
+with open(wav, "rb") as fh:
+    m.add_attachment(fh.read(), maintype="audio", subtype="x-wav", filename="msg0003.wav")
+sys.stdout.buffer.write(m.as_bytes())