Add OpenProject Gitea integration plugin

Implements a Gitea integration for OpenProject following the same
patterns as the bundled GitHub and GitLab integrations.

- Webhook endpoint at /webhooks/gitea with HMAC-SHA256 verification
- Handles pull_request and issue_comment events
- Links Gitea PRs to work packages via OP# references or URLs
- Posts journal comments on WPs for PR lifecycle events
- Gitea tab on the work package split view
- V3 API endpoint: GET /api/v3/work_packages/:id/gitea_pull_requests
- Admin settings UI for bot user and webhook secret
- Nightly cron job to clean up unlinked PR records

frontend/module/main.ts

@@ -0,0 +1,93 @@
+//-- copyright
+// OpenProject is an open source project management software.
+// Copyright (C) the OpenProject GmbH
+//
+// This program is free software; you can redistribute it and/or
+// modify it under the terms of the GNU General Public License version 3.
+//
+// OpenProject is a fork of ChiliProject, which is a fork of Redmine. The copyright follows:
+// Copyright (C) 2006-2013 Jean-Philippe Lang
+// Copyright (C) 2010-2013 the ChiliProject Team
+//
+// This program is free software; you can redistribute it and/or
+// modify it under the terms of the GNU General Public License
+// as published by the Free Software Foundation; either version 2
+// of the License, or (at your option) any later version.
+//
+// This program is distributed in the hope that it will be useful,
+// but WITHOUT ANY WARRANTY; without even the implied warranty of
+// MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+// GNU General Public License for more details.
+//
+// You should have received a copy of the GNU General Public License
+// along with this program; if not, write to the Free Software
+// Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA  02110-1301, USA.
+//
+// See docs/COPYRIGHT.rdoc for more details.
+//++
+
+import { Injector, NgModule, inject } from '@angular/core';
+import { OpSharedModule } from 'core-app/shared/shared.module';
+import { OpenprojectTabsModule } from 'core-app/shared/components/tabs/openproject-tabs.module';
+import { WorkPackageTabsService } from 'core-app/features/work-packages/components/wp-tabs/services/wp-tabs/wp-tabs.service';
+
+import { GiteaTabComponent } from './gitea-tab/gitea-tab.component';
+import { TabPrsComponent } from './tab-prs/tab-prs.component';
+import { PullRequestComponent } from './pull-request/pull-request.component';
+import { WorkPackageResource } from 'core-app/features/hal/resources/work-package-resource';
+import { Observable } from 'rxjs';
+import { map } from 'rxjs/operators';
+import { HalResourceService } from 'core-app/features/hal/services/hal-resource.service';
+import { ApiV3Service } from 'core-app/core/apiv3/api-v3.service';
+import { CollectionResource } from 'core-app/features/hal/resources/collection-resource';
+
+export function workPackageGiteaCount(
+  workPackage:WorkPackageResource,
+  injector:Injector,
+):Observable<number> {
+  const halResourceService = injector.get(HalResourceService);
+  const apiV3Service = injector.get(ApiV3Service);
+  const basePath = apiV3Service.work_packages.id(workPackage.id as string).path;
+
+  return halResourceService
+    .get<CollectionResource>(basePath + '/gitea_pull_requests')
+    .pipe(map((collection) => collection.count));
+}
+
+export function initializeGiteaIntegrationPlugin(injector:Injector) {
+  const wpTabService = injector.get(WorkPackageTabsService);
+  wpTabService.registerBefore(
+    'watchers',
+    {
+      component: GiteaTabComponent,
+      name: I18n.t('js.gitea_integration.work_packages.tab_name'),
+      id: 'gitea',
+      displayable: (workPackage) => !!workPackage.gitea,
+      count: workPackageGiteaCount,
+    },
+  );
+}
+
+@NgModule({
+  imports: [
+    OpSharedModule,
+    OpenprojectTabsModule,
+  ],
+  declarations: [
+    GiteaTabComponent,
+    TabPrsComponent,
+    PullRequestComponent,
+  ],
+  exports: [
+    GiteaTabComponent,
+    TabPrsComponent,
+    PullRequestComponent,
+  ],
+})
+export class PluginModule {
+  constructor() {
+    const injector = inject(Injector);
+
+    initializeGiteaIntegrationPlugin(injector);
+  }
+}