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/pull-request/pull-request.component.html

@@ -0,0 +1,50 @@
+<div
+  class="op-pull-request--title"
+  [textContent]="pullRequest.title"
+></div>
+
+<span class="op-pull-request--state" [ngClass]="'op-pull-request--state_' + state">
+  {{ state }} |
+  <a
+    [ngClass]="'op-pull-request--link_' + state"
+    [href]="pullRequest.htmlUrl"
+    target="_blank"
+    rel="noopener noreferrer"
+    [textContent]="pullRequest.repository + '#' + pullRequest.number"
+  ></a>
+</span>
+
+@if (pullRequest.labels && pullRequest.labels.length > 0) {
+  <button (click)="toggleLabels(pullRequest.number)" class="op-pull-request--label_icon" title="Show/Hide labels">
+    Labels
+  </button>
+}
+
+<div class="op-pull-request--info_created">
+  {{ text.label_created_by }}
+  <span class="op-pull-request--user">
+    @if (pullRequest.giteaUser) {
+      <span
+        class="op-pull-request--username"
+        [textContent]="pullRequest.giteaUser.login"
+      ></span>
+    }
+  </span>
+  <span class="op-pull-request--date">
+    {{ text.label_last_updated_on }}
+    <op-date-time [dateTimeValue]="pullRequest.gitea_updated_at" />
+  </span>.
+</div>
+
+<div
+  class="op-pull-request--labels"
+  [ngClass]="'op-pull-request--labels-' + pullRequest.number"
+  style="display: none;">
+  @for (label of pullRequest.labels; track label) {
+    <span>
+      <span class="op-pull-request--label" [ngStyle]="{'background-color': label.color}">
+        {{ label.name }}
+      </span>
+    </span>
+  }
+</div>

frontend/module/pull-request/pull-request.component.ts

@@ -0,0 +1,66 @@
+//-- 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 { Component, Input, inject, ChangeDetectionStrategy } from '@angular/core';
+import { PathHelperService } from 'core-app/core/path-helper/path-helper.service';
+import { I18nService } from 'core-app/core/i18n/i18n.service';
+import { IGiteaPullRequestResource } from 'core-app/features/plugins/linked/openproject-gitea_integration/typings';
+
+@Component({
+  selector: 'gitea-pull-request',
+  templateUrl: './pull-request.component.html',
+  host: { class: 'op-pull-request' },
+  changeDetection: ChangeDetectionStrategy.Eager,
+  standalone: false,
+})
+export class PullRequestComponent {
+  readonly PathHelper = inject(PathHelperService);
+  readonly I18n = inject(I18nService);
+
+  @Input() public pullRequest:IGiteaPullRequestResource;
+
+  public text = {
+    label_created_by: this.I18n.t('js.label_created_by'),
+    label_last_updated_on: this.I18n.t('js.gitea_integration.updated_on'),
+  };
+
+  get state():string {
+    if (this.pullRequest.state === 'open') {
+      return this.pullRequest.draft ? 'draft' : 'open';
+    }
+    return this.pullRequest.merged ? 'merged' : 'closed';
+  }
+
+  toggleLabels(identifier:number|undefined):void {
+    if (identifier === undefined) return;
+    const el = document.querySelector(`.op-pull-request--labels-${identifier}`) as HTMLElement|null;
+    if (el) {
+      el.style.display = el.style.display === 'none' ? 'block' : 'none';
+    }
+  }
+}