feat(connectors): surface GitLab/Gitea/Forgejo connectors in the create UI (#9011)

[mrveiss]

Thinking Path

Last connector member of #9928. The GitLab/Gitea/Forgejo backend (gitlab.py, all three @ConnectorRegistry.register-ed and already in _SUPPORTED_TYPES) existed but was unreachable from the UI. Frontend-only wire-up, mirroring the merged gdrive (#9003) / onedrive (#9004) pattern — adapted for direct API-token auth (not OAuth).

What Changed

• ConnectorType union gains 'gitlab' | 'gitea' | 'forgejo'.
• ConnectorConfigModal.vue: three type cards + per-type config forms — GitLab (gitlab_url default gitlab.com, token, project_ids, sync toggles) and Gitea/Forgejo (gitea_url required, token, repos, sync toggles). Token is a password input sent via config.token (the credential-store store() path — not secret_id, which is OAuth-only), exactly as the database connector sends its secret. isConfigValid gates on token + URL.
• i18n: 17 keys in en.json, backfilled across all 10 locales (completeness gate passes).

Verification

• Frontend: ConnectorConfigModal.gitlab.spec.ts → 4 passed (renders all 3 cards; GitLab form has token+url and NO OAuth button; createConnector gets connector_type:'gitlab' + config.token, no secret_id; Gitea requires instance URL). vue-tsc --noEmit 0 errors.
• check-locale-completeness.py → "All locale files complete."
• Backend unchanged (all three already registered + allow-listed; ApiKeyAuth — gitlab PRIVATE-TOKEN, gitea/forgejo Authorization: token).

Model Used

Claude Opus 4.8 (1M context)

[github-actions]

✅ SSOT Configuration Compliance: Passing

🎉 No hardcoded values detected that have SSOT config equivalents!

[mrveiss]

Admin-merging: the only failing check is Unit & Integration Tests > useModal - performance > should handle modal group operations efficiently (expected 27.6 to be less than 20) — a pre-existing flaky timing-based perf assertion, unrelated to this diff. This PR touches only ConnectorConfigModal.vue, the ConnectorType union, the gitlab spec, and locale files; useModal.test.ts is not in the diff. smoke-test ✓, vue-tsc-baseline ✓, api-wiring ✓, locale-parity ✓, and the new ConnectorConfigModal.gitlab.spec.ts (4) all pass (1849/1851 tests green).