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.

docs/gates.md

@@ -55,7 +55,6 @@ them itself (`no-undef`, `no-redeclare`, `no-dupe-keys`, …), nor the formattin
 | e2e | `@typescript-eslint/no-floating-promises` — narrowed | The same `allowForKnownSafeCalls` list (the typed rules are one object for both scopes). | 6 names |
 | lib/http.ts | `no-restricted-globals` — narrowed | A network owner (`NETWORK_OWNERS` in eslint.config.js): the one module that may call `fetch` (`send`, which `req` and the public pages go through). Every other network global stays restricted there. | 1 global |
 | lib/api/core.ts | `no-restricted-globals` — narrowed | A network owner: `uploadReq` is the one `XMLHttpRequest` (upload progress). | 1 global |
-| lib/messagesSocket.ts | `no-restricted-globals` — narrowed | A network owner: the chat socket is the one `WebSocket`. | 1 global |
 | src tests · ui tests · lib tests | `no-restricted-globals`, `no-restricted-properties` — off | A test stands a double in for the network (`vi.stubGlobal("fetch", …)`) and may reach it directly. | — |
 | src tests · ui tests · lib tests | `local/literal-a11y-text`, `local/button-primitive`, `local/input-primitive`, `local/surface-role`, `local/glyph-link` — off | A test renders throwaway markup (a raw button as a focus target, an untranslated label) that is not product UI. | — |
 | FocusSafeButton.tsx + AnchoredPopover.tsx | `local/focus-safe-disabled` — off | FocusSafeButton: it IS the focus-safe primitive the rule points everyone else to. | — |