merge: resolve v1.21.1 conflicts with custom

Resolve all 10 upstream v1.21.1 merge conflicts into custom, keeping
custom's GitLab/Gitea forge customizations layered on upstream while
lifting upstream improvements. Restored tr.ts i18n key parity with the
custom en.ts dictionary (471 custom forge keys added, en fallback) so the
upstream-introduced locale stays in parity.

Also stage bun.lock version alignment (1.21.0 -> 1.21.1) that matches the
staged package.json bump.

Verification: ui + web type-check pass; ui/web tests pass except
pre-existing failures on the custom baseline (forge.test.ts, session-actions,
issue-1637-2270, routes.test.js fs-stat directory scope).

package.json

@@ -80,6 +80,7 @@
     "icons:sprite": "node scripts/generate-file-type-sprite.mjs",
     "icons:generate": "bun run scripts/generate-icon-sprite.mjs",
     "themes:port:opencode": "tsx scripts/port-opencode-theme.ts",
+    "gitea:live-test": "bun packages/web/scripts/gitea-live-test.ts",
     "version:bump": "node scripts/bump-version.mjs",
     "release:prepare": "bun run build && bun run type-check && bun run lint",
     "release:test": "./scripts/test-release-build.sh",