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/App.tsx

@@ -35,7 +35,6 @@ import BackToTop from "./components/ui/BackToTop";
 import PageShell from "./components/ui/PageShell";
 import { SkipLink } from "./components/ui/SkipLink";
 import { pageTitleKey } from "./lib/pageMeta";
-import ChatDock from "./components/ChatDock";
 import DebugRecorder from "./components/DebugRecorder";
 import Toaster from "./components/ui/Toaster";
 import KeyboardHelp from "./components/ui/KeyboardHelp";
@@ -459,7 +458,6 @@ export default function App() {
           "take me to X" the same way. Their keys are bound by useGlobalKeymap above. */}
       <KeyboardHelp />
       <AppCommandPalette />
-      {me && !me.is_demo && <ChatDock meId={me.id} />}
       {/* The debug recorder (E16): its start dialog, and its pill docked under the toasts. */}
       {me && !me.is_demo && <DebugRecorder />}
       <Suspense fallback={null}>