fix(logout): no draft or search opt-in left behind after logout (#319, #296)

- #319: logout wiped the drafts, then reloaded, and the reload's pagehide
  made RoomInput flush the open composer's (decrypted) draft straight back
  to localStorage. clearPlaintextCaches now sets a module flag and
  persistDraft stops writing once it's set (resets with the new page).
- #296: the device-wide encrypted-search opt-in (searchCacheEnabled)
  survived logout, so the next account started indexing decrypted text
  without opting in. It's now cleared, along with the SDK's per-user
  filter key.

Verified headless with a throwaway account (search opt-in on, "SECRET
half-typed reply" in the composer, Settings → Log out): before, the draft
and searchCacheEnabled=true remained; now neither does. Unit test added.

Fixes #319
Fixes #296

Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_017PCb59uY3UKqDqt7B6hzd5

src/app/features/room/RoomInput.tsx

@@ -160,6 +160,7 @@ import { scheduledMessagesAtom } from '../../state/scheduledMessages';
 import { createErrorToast, toastQueueAtom } from '../../state/toast';
 import { getThreadDraftKey } from '../../state/room/thread';
 import { stripTrackingParamsInHtml, stripTrackingParamsInText } from '../../utils/urlTracking';
+import { plaintextCachesWiped } from '../../state/plaintextCaches';
 
 const GifPicker = React.lazy(() =>
   import('../../components/GifPicker').then((m) => ({ default: m.GifPicker })),
@@ -562,6 +563,8 @@ export const RoomInput = forwardRef<HTMLDivElement, RoomInputProps>(
     // Persist the current editor state to the draft atom + localStorage; an empty
     // editor clears both so the draft indicators never claim a draft that isn't there.
     const persistDraft = useCallback(() => {
+      // [Gitea #319] Logout already wiped the drafts; don't write this one back.
+      if (plaintextCachesWiped()) return;
       if (!isEmptyEditor(editor)) {
         const parsedDraft = JSON.parse(JSON.stringify(editor.children));
         setMsgDraft(parsedDraft);