feat(web): add GitLab issues/MRs server module

Add a server-side GitLab integration mirroring the GitHub module:
- auth.js: PAT auth storage with multi-account support and configurable
  base URL (gitlab.com default, self-hosted instances supported)
- client.js: raw-fetch GitLab REST v4 client with per-request timeout,
  ETag conditional-GET cache, own rate-limit cooldown, pagination, and
  single-follow redirect handling
- repo.js: GitLab remote URL parser + directory resolution
- routes.js: read-only /api/gitlab/* routes (auth, issues, MRs, branches)
- index.js + DOCUMENTATION.md + unit tests for auth, client, repo, routes
- Wire registerGitLabRoutes into feature-routes-runtime

packages/web/server/lib/opencode/feature-routes-runtime.js

@@ -4,6 +4,7 @@ import { registerSmallModelRoutes } from '../small-model/routes.js';
 import { registerWalkthroughRoutes } from '../walkthrough/routes.js';
 import { registerSessionGoalRoutes } from '../session-goal/routes.js';
 import { registerGitHubRoutes } from '../github/routes.js';
+import { registerGitLabRoutes } from '../gitlab/routes.js';
 import { registerGitRoutes } from '../git/routes.js';
 import { registerDevServerRoutes } from '../dev-servers/routes.js';
 import { registerMagicPromptRoutes } from '../magic-prompts/routes.js';
@@ -297,6 +298,7 @@ export const createFeatureRoutesRuntime = (dependencies) => {
     registerWalkthroughRoutes(app, { getWalkthroughService });
     registerSessionGoalRoutes(app);
     registerGitHubRoutes(app);
+    registerGitLabRoutes(app);
     registerGitRoutes(app);
     registerDevServerRoutes(app, { scanner: devServerScanner, getOwnPorts });
     registerMagicPromptRoutes(app, {