fix: rewrite Tekton integration tests for X-Service routing

FIXES:
- Remove stale files: k8s/argocd-apps/, k8s/tekton/base/, overlays/
  (Tekton infra is in homelab repo, not here)
- Fix step.resources → step.computeResources (Tekton v1 API)
- Fix Task: use curl sidecar pattern instead of distroless image
  (distroless has no shell/curl/go)
- Fix routing: use X-Service + X-Resource headers, not path-based
- Extract test script to scripts/integration-test.sh (ConfigMap mount)
- Install kubectl in CI runner (was missing)
- Prune README to essentials

TASK ARCHITECTURE:
  sidecar: gateway image (mounts config secret, runs on localhost)
  step: curlimages/curl (runs integration-test.sh from ConfigMap)

TEST COVERAGE:
  health, header validation, memory, s3, sqs, workflow, iam

k8s/tekton/pipeline-integration-test.yaml

@@ -7,29 +7,24 @@ metadata:
     app: api-gateway
     component: testing
 spec:
-  description: Pipeline to run integration tests for API gateway
+  description: >
+    Run integration tests against a gateway image.
+    Spins up the image as a sidecar, tests via curl, reports pass/fail.
   params:
   - name: image
     type: string
-    description: Container image to test (repo:tag)
-    default: "forgejo.riotpiao.com/rock/api-gateway:latest"
-  - name: test-timeout
-    type: string
-    default: "5m"
-    description: Test execution timeout
+    description: "Container image to test (repo:sha)"
   results:
   - name: test-result
-    description: Overall test result (pass/fail)
-    value: $(tasks.run-integration-tests.results.result)
-  - name: test-message
-    description: Test summary message
-    value: $(tasks.run-integration-tests.results.message)
+    description: "pass or fail"
+    value: $(tasks.integration-test.results.result)
+  - name: test-summary
+    description: "e.g. 8/8 passed"
+    value: $(tasks.integration-test.results.summary)
   tasks:
-  - name: run-integration-tests
+  - name: integration-test
     taskRef:
       name: integration-test
     params:
     - name: image
       value: $(params.image)
-    - name: timeout
-      value: $(params.test-timeout)