chore: remove Sentry.io entirely

We no longer use Sentry. Removed:
- @sentry/react + @sentry/vite-plugin (package.json + lockfile)
- Sentry.init in index.tsx and the VITE_SENTRY_DSN env (.env.production)
- @sentry/vite-plugin + the SENTRY_AUTH_TOKEN sourcemap-upload path in
  vite.config.js (sourcemap now always false) and the CI env var
- Sentry.ErrorBoundary in App.tsx -> react-error-boundary's ErrorBoundary with a
  folds-native fallback (Box/Text/Button + config tokens), which also resolves
  the native-cinny audit's raw-#hex/#5865f2 fallback finding.

Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>

package.json

@@ -45,7 +45,6 @@
     "@giphy/js-util": "5.2.0",
     "@giphy/react-components": "10.1.2",
     "@sapphi-red/web-noise-suppressor": "0.3.5",
-    "@sentry/react": "10.53.1",
     "@tanstack/react-query": "5.100.13",
     "@tanstack/react-query-devtools": "5.100.13",
     "@tanstack/react-virtual": "3.13.25",
@@ -105,7 +104,6 @@
     "@element-hq/element-call-embedded": "0.20.1",
     "@rollup/plugin-inject": "5.0.5",
     "@rollup/plugin-wasm": "6.2.2",
-    "@sentry/vite-plugin": "5.3.0",
     "@types/chroma-js": "3.1.2",
     "@types/file-saver": "2.0.7",
     "@types/is-hotkey": "0.1.10",