chore: Update CI workflow and testing setup with new dependencies and test plan documentation

This commit enhances the CI workflow by adding steps to create test databases and install new testing dependencies, including `pytest`, `httpx`, and `pytest-cov`. Additionally, comprehensive test plan documentation is introduced to outline the structure and best practices for backend API tests. These changes improve the testing environment and contribute to a more robust CI process.

.gitea/workflows/ci.yml

@@ -184,7 +184,7 @@ jobs:
         run: |
           apt-get update && apt-get install -y postgresql-client
           pip install --no-cache-dir -r requirements.txt
-          pip install --no-cache-dir pytest httpx
+          pip install --no-cache-dir pytest httpx pytest-cov
 
       - name: Audit Python dependencies
         run: |
@@ -192,10 +192,19 @@ jobs:
           pip-audit --desc || true
         continue-on-error: true
 
+      - name: Create test databases
+        run: |
+          export PGPASSWORD=postgres
+          psql -h postgres -U postgres -c "CREATE DATABASE punimtag_test;" || true
+          psql -h postgres -U postgres -c "CREATE DATABASE punimtag_auth_test;" || true
+          echo "✅ Test databases ready"
+
       - name: Initialize database schemas
         run: |
           export PYTHONPATH=$(pwd)
+          echo "🗃️  Initializing main database schema..."
           python -c "from backend.db.models import Base; from backend.db.session import engine; Base.metadata.create_all(bind=engine)"
+          echo "✅ Main database schema initialized"
           python << 'EOF'
           # Initialize auth database schema without importing worker (avoids DeepFace/TensorFlow imports)
           from backend.db.session import auth_engine
@@ -365,8 +374,20 @@ jobs:
       - name: Run backend tests
         run: |
           export PYTHONPATH=$(pwd)
-          python -m pytest tests/ -v || true
+          echo "🧪 Running all backend API tests..."
+          python -m pytest tests/ -v --tb=short --cov=backend --cov-report=term-missing --cov-report=xml --junit-xml=test-results.xml || true
         continue-on-error: true
+      
+      - name: Test results summary
+        if: always()
+        run: |
+          echo "## 📊 Test Results Summary" >> $GITHUB_STEP_SUMMARY || true
+          echo "" >> $GITHUB_STEP_SUMMARY || true
+          if [ -f test-results.xml ]; then
+            echo "✅ Test results generated (JUnit XML)" >> $GITHUB_STEP_SUMMARY || true
+          fi
+          echo "" >> $GITHUB_STEP_SUMMARY || true
+          echo "Run \`pytest tests/ -v\` locally to see detailed results." >> $GITHUB_STEP_SUMMARY || true
 
   build:
     needs: skip-ci-check