feat(privacy): strip tracking parameters from links on paste, send and render (#103)

Shared links routinely carry ad/analytics identifiers (utm_*, fbclid, gclid,
YouTube si=, Amazon ref=/tag=, X s=/t=, TikTok _r/_t, …) that tie every
recipient's click back to the person who shared the link. New
src/app/utils/urlTracking.ts is a pure, local stripper: a global list +
utm_/pk_/matomo_ prefixes, plus host-scoped rules so e.g. `si` is only
removed on youtube/spotify. matrix.to and non-http(s) schemes are never
rewritten; unparseable input is returned unchanged; Amazon's `th`/`psc`
variant selectors are deliberately kept. 13 unit tests.

Wired at three points, all behind a new Settings → Privacy toggle
(`stripTrackingParams`, default on):
- paste: plain-text pastes are cleaned and re-inserted through Slate's own
  insertData so multi-line pastes still split into paragraphs;
- send: RoomInput submit + schedule paths and MessageEditor saves clean both
  `body` and `formatted_body` (the HTML variant unescapes `&` around each
  URL and re-escapes it so the markup is untouched);
- render: linkify `formatHref`/`format` and explicit `<a href>` in
  formatted_body are cleaned, so links sent from other clients are safe to
  click too. LINKIFY_OPTS is spread into memoised per-timeline objects, so
  the toggle is a module flag kept current by ClientNonUIFeatures.

Co-Authored-By: Claude Opus 5 <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_01PPmy3tPq869XDW4njjVaKA

src/app/pages/client/ClientNonUIFeatures.tsx

@@ -20,6 +20,7 @@ import { notificationPermission, setFavicon, showOsNotification } from '../../ut
 import { NOTIFICATION_SOUND_MAP } from '../../utils/notificationSounds';
 import { useSetting } from '../../state/hooks/settings';
 import { settingsAtom } from '../../state/settings';
+import { setStripTrackingOnRender } from '../../plugins/react-custom-html-parser';
 import { allInvitesAtom } from '../../state/room-list/inviteList';
 import { useMatrixClient } from '../../hooks/useMatrixClient';
 import { useHydrateMsgDrafts } from '../../hooks/useHydrateMsgDrafts';
@@ -90,6 +91,11 @@ function SystemEmojiFeature() {
 
 function PageZoomFeature() {
   const [pageZoom] = useSetting(settingsAtom, 'pageZoom');
+  // [Gitea #103] Mirror the privacy toggle into the html parser's module flag.
+  const [stripTracking] = useSetting(settingsAtom, 'stripTrackingParams');
+  useEffect(() => {
+    setStripTrackingOnRender(stripTracking);
+  }, [stripTracking]);
 
   if (pageZoom === 100) {
     document.documentElement.style.removeProperty('font-size');