feat!: remove direct messaging (chat)

E2EE direct messages, the chat dock, the Messages module, the message
WebSocket and its realtime registry, and the messages / message_keys
tables (migration 0097; the downgrade restores the empty schema). Prod
held two welcome notes, no message between people and one key — never
used (owner decision, E34). WebSocket now has no owner module: the lint
bans it everywhere. Privacy policy updated: it no longer promises E2EE
for a feature that is gone.

scripts/audit_metrics.py

@@ -146,7 +146,8 @@ def _footprint(
     patterns = {
         "demo_files": re.compile(r"\bdemo|isDemo|is_demo", re.IGNORECASE),
         "chat_files": re.compile(r"\bchat\b|\bmessages?\.py|\bChat[A-Z]|message_keys"),
-        "access_request_files": re.compile(r"access[ _-]?request|AccessRequest", re.IGNORECASE),
+        # the public form, not the admin's access-request queue (that stays)
+        "access_request_form_files": re.compile(r"request[-_]access|requestAccess|AccessRequestIn"),
     }
     return {
         k: sum(1 for _, ls in be + fe if any(rx.search(ln) for ln in ls))