fix(ci): 将Validate/Frontend等job从ci-check迁移到ci-l2 runner，解决ci-check环境Docker端口映射失效问题

ci-check runner的Docker-in-Docker端口映射存在问题，容器内部pg_isready显示healthy
但宿主侧TCP连接始终失败（60秒超时），导致Validate Code Quality的Alembic迁移验证
以及所有需要独立PG/Redis容器的检查失败。

将所有ci-check runner的job统一迁移到ci-l2（与Integration Tests同环境），
ci-l2的Docker网络端口映射工作正常，确保所有需要容器的检查能稳定运行。

影响的job:
- check-frontend-only
- Validate Code Quality And Tests
- Frontend Lint
- Frontend Unit Tests

.gitea/workflows/ci-pipeline.yml

@@ -24,7 +24,7 @@ concurrency:
 jobs:
   check-frontend-only:
     name: Check if frontend-only change
-    runs-on: ci-check
+    runs-on: ci-l2
     if: github.event_name == 'pull_request'
     outputs:
       skip_backend: ${{ steps.check.outputs.skip_backend }}
@@ -68,7 +68,7 @@ jobs:
     needs: check-frontend-only
     if: always() && needs.check-frontend-only.outputs.skip_backend != 'true'
     name: Validate Code Quality And Tests
-    runs-on: ci-check
+    runs-on: ci-l2
     timeout-minutes: 10
     permissions:
       contents: write
@@ -232,7 +232,7 @@ jobs:
 
   frontend-lint:
     name: Frontend Lint
-    runs-on: ci-check
+    runs-on: ci-l2
     timeout-minutes: 10
     steps:
     - name: Checkout code
@@ -275,7 +275,7 @@ jobs:
 
   frontend-unit-test:
     name: Frontend Unit Tests
-    runs-on: ci-check
+    runs-on: ci-l2
     timeout-minutes: 15
     needs: check-frontend-only
     if: always() && needs.check-frontend-only.outputs.skip_frontend != 'true'