fix: use PostgreSQL service container in CI instead of Testcontainers

Testcontainers can't network properly on TrueNAS act-runner (host network vs bridge). Added postgres:16-alpine service container to CI workflow and made AbstractIntegrationTest conditionally skip Testcontainers when CI_POSTGRES_URL env var is present.

.gitea/workflows/ci.yml

@@ -19,6 +19,20 @@ jobs:
   # ─────────────────────────────────────────────────────────────────────────────
   backend:
     runs-on: ubuntu-latest
+    services:
+      postgres:
+        image: postgres:16-alpine
+        env:
+          POSTGRES_DB: cannamanage_test
+          POSTGRES_USER: test
+          POSTGRES_PASSWORD: test
+        ports:
+          - 5432:5432
+        options: >-
+          --health-cmd pg_isready
+          --health-interval 10s
+          --health-timeout 5s
+          --health-retries 5
     steps:
       - uses: actions/checkout@v4
 
@@ -34,6 +48,10 @@ jobs:
 
       - name: Maven test
         run: ./mvnw test -B -T 1C
+        env:
+          CI_POSTGRES_URL: jdbc:postgresql://localhost:5432/cannamanage_test
+          CI_POSTGRES_USER: test
+          CI_POSTGRES_PASSWORD: test
 
       - name: OWASP Dependency-Check (SCA)
         run: |