refactor: use in-cluster authentication instead of kubeconfig secret

RATIONALE:
Gitea CI runner is running IN-CLUSTER, so we should use Kubernetes' built-in
in-cluster authentication mechanism instead of storing kubeconfig secrets.

IN-CLUSTER AUTHENTICATION:
- Kubernetes automatically mounts service account token
- Location: /var/run/secrets/kubernetes.io/serviceaccount/token
- Location: /var/run/secrets/kubernetes.io/serviceaccount/ca.crt
- kubectl automatically detects and uses these
- No need to pass credentials via secrets

CHANGES:
1. Remove KUBECONFIG_B64 secret requirement
2. Add in-cluster auth detection step
3. Update Job to use actual built image (not golang base)
4. Job uses imagePullSecrets for registry auth (can be encrypted with SOPS)
5. Add regcred image pull secret reference

CI FLOW:
  1. Detect in-cluster authentication is available
  2. kubectl commands automatically use mounted service account
  3. No secrets needed in CI env vars
  4. Job applies with RBAC service account
  5. Registry credentials via imagePullSecrets (encrypted with SOPS)

SECURITY:
✓ In-cluster auth is more secure (bound to service account)
✓ No kubeconfig stored in secrets
✓ Sensitive data encrypted with SOPS
✓ Principle of least privilege (service account RBAC)

.gitea/workflows/ci.yaml

@@ -55,41 +55,46 @@ jobs:
           docker push "${IMAGE}:${{ steps.sha.outputs.short_sha }}"
           echo "✓ Pushed test image: ${IMAGE}:${{ steps.sha.outputs.short_sha }}"
 
-      - name: Setup kubeconfig for integration test job
+      - name: Detect in-cluster Kubernetes authentication
         run: |
-          mkdir -p ~/.kube
-          echo "${KUBECONFIG_B64}" | base64 -d > ~/.kube/config
-        env:
-          KUBECONFIG_B64: ${{ secrets.KUBECONFIG_B64 }}
-        continue-on-error: true
+          # When running inside K8s cluster, kubectl auto-detects service account
+          # Mounted at: /var/run/secrets/kubernetes.io/serviceaccount/
+          if [ -f /var/run/secrets/kubernetes.io/serviceaccount/token ]; then
+            echo "✓ In-cluster authentication detected"
+            export KUBECONFIG=/dev/null  # kubectl will auto-use in-cluster auth
+          else
+            echo "⚠ Not running in-cluster, kubectl may fail"
+          fi
 
       - name: Run integration tests via Kubernetes Job
         run: |
           echo "Running integration tests via Kubernetes Job..."
-          echo "Image: ${IMAGE}:${{ steps.sha.outputs.short_sha }}"
+          echo "Test image: ${IMAGE}:${{ steps.sha.outputs.short_sha }}"
           
-          # Apply job template from repo
+          # Apply job template from repo (uses in-cluster auth automatically)
           kubectl apply -f k8s/integration-test-job.yaml
           
           # Update job to use new image
           kubectl set image job/api-gateway-integration-test \
-            api-gateway="${IMAGE}:${{ steps.sha.outputs.short_sha }}" \
+            integration-tester="${IMAGE}:${{ steps.sha.outputs.short_sha }}" \
             -n api --record
           
-          # Wait for job to complete (max 5 minutes)
-          echo "Waiting for job to complete..."
+          # Wait for job to complete (max 10 minutes)
+          echo "Waiting for job to complete (this may take a few minutes)..."
           kubectl wait --for=condition=complete job/api-gateway-integration-test \
-            -n api --timeout=5m || true
+            -n api --timeout=10m 2>/dev/null || true
           
           # Stream logs
-          echo "Job logs:"
-          kubectl logs -n api job/api-gateway-integration-test --all-containers=true --timestamps=true || true
+          echo ""
+          echo "=== Job Logs ==="
+          kubectl logs -n api job/api-gateway-integration-test --all-containers=true --timestamps=true || echo "No logs available"
+          echo "================"
+          echo ""
           
           # Check if job succeeded
-          SUCCEEDED=$(kubectl get job api-gateway-integration-test -n api -o jsonpath='{.status.succeeded}')
-          FAILED=$(kubectl get job api-gateway-integration-test -n api -o jsonpath='{.status.failed}')
+          SUCCEEDED=$(kubectl get job api-gateway-integration-test -n api -o jsonpath='{.status.succeeded}' 2>/dev/null || echo "0")
+          FAILED=$(kubectl get job api-gateway-integration-test -n api -o jsonpath='{.status.failed}' 2>/dev/null || echo "0")
           
-          echo ""
           echo "Job Status: Succeeded=$SUCCEEDED, Failed=$FAILED"
           
           if [ "$SUCCEEDED" = "1" ]; then