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.

frontend/src/lib/api.ts

@@ -58,8 +58,6 @@ export {
   parsePlexFilters,
   isIntrinsicReadOnly,
 } from "./api/plex";
-import { messagingApi } from "./api/messaging";
-export type * from "./api/messaging";
 import { downloadsApi } from "./api/downloads";
 export type * from "./api/downloads";
 import { debugSessionsApi, diagnosticsApi } from "./api/diagnostics";
@@ -81,7 +79,6 @@ export const api = {
   ...quotaApi,
   ...adminApi,
   ...plexApi,
-  ...messagingApi,
   ...downloadsApi,
   ...diagnosticsApi,
   ...debugSessionsApi,