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

config/locales/en.yml

@@ -0,0 +1,92 @@
+#-- 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 COPYRIGHT and LICENSE files for more details.
+#++
+
+---
+en:
+  activerecord:
+    attributes:
+      gitea_pull_request:
+        labels: "Labels"
+    errors:
+      models:
+        gitea_pull_request:
+          attributes:
+            labels:
+              invalid_schema: "must be an array of hashes with keys: color, name"
+    models:
+      gitea_pull_request:
+        one: "Gitea pull request"
+        other: "Gitea pull requests"
+      gitea_user:
+        one: "Gitea user"
+        other: "Gitea users"
+  attributes:
+    gitea: "Gitea identifier"
+    gitea_avatar_url: "Avatar URL"
+    gitea_html_url: "Gitea HTML URL"
+    gitea_login: "Gitea login"
+    gitea_name: "Gitea name"
+    gitea_pull_request: "Pull Request"
+    gitea_updated_at: "Updated at"
+  gitea_integration:
+    pull_request_opened_comment: >
+      **PR Opened:** Pull request %{pr_number} [%{pr_title}](%{pr_url}) for [%{repository}](%{repository_url})
+      has been opened by [%{gitea_user}](%{gitea_user_url}).
+    pull_request_closed_comment: >
+      **PR Closed:** Pull request %{pr_number} [%{pr_title}](%{pr_url}) for [%{repository}](%{repository_url})
+      has been closed by [%{gitea_user}](%{gitea_user_url}).
+    pull_request_merged_comment: >
+      **PR Merged:** Pull request %{pr_number} [%{pr_title}](%{pr_url}) for [%{repository}](%{repository_url})
+      has been merged by [%{gitea_user}](%{gitea_user_url}).
+    pull_request_reopened_comment: >
+      **PR Reopened:** Pull request %{pr_number} [%{pr_title}](%{pr_url}) for [%{repository}](%{repository_url})
+      has been reopened by [%{gitea_user}](%{gitea_user_url}).
+    issue_comment_referenced_comment: >
+      **Referenced in Comment:** [%{gitea_user}](%{gitea_user_url}) referenced this work package in a
+      [comment](%{comment_url}) on issue %{issue_number} [%{issue_title}](%{comment_url})
+      in [%{repository}](%{repository_url}):
+
+      %{comment_body}
+
+  label_gitea_actor: "Gitea actor"
+  label_gitea_integration: "Gitea Integration"
+  label_gitea_webhook_secret: "Webhook secret"
+  permission_show_gitea_content: "Show Gitea content"
+  project_module_gitea: "Gitea"
+  text_gitea_actor_info: >
+    The OpenProject user whose API key must be used to authenticate incoming webhook requests.
+    When set, requests authenticated with any other user's credentials are rejected.
+    This user also posts automated comments on work packages. Defaults to the system user when not set.
+  text_gitea_webhook_secret_info: >
+    A secret token shared with Gitea when configuring the webhook.
+    When set, OpenProject verifies the X-Gitea-Signature header on every incoming request,
+    rejecting payloads that do not match. Leave blank to skip verification (not recommended).
+  text_gitea_webhook_secret_missing_warning: >
+    No webhook secret is configured. Any request to the Gitea webhook endpoint will be accepted
+    without verification, which may allow unauthorized actors to forge events. It is strongly
+    recommended to set a secret.