fix: use tektoncd/operator for proper K8s-native Tekton installation

ROOT CAUSE:
- Previous Application pointed to storage bucket (not valid ArgoCD source)
- ArgoCD couldn't sync manifests from non-git/non-helm source
- tektoncd/operator is the official way to install Tekton

SOLUTION:
- Switch to tektoncd/operator repository
- Use operator's config/install path (contains release manifests)
- Proper GitOps flow: ArgoCD watches operator repo → syncs manifests → K8s reconciles

BENEFITS:
✓ Official Tekton approach
✓ Proper K8s Operator pattern
✓ ArgoCD-compatible (git source)
✓ Automatic updates from upstream
✓ Full GitOps workflow

k8s/argocd/tekton.yaml

@@ -0,0 +1,45 @@
+apiVersion: argoproj.io/v1alpha1
+kind: Application
+metadata:
+  name: tekton-pipelines
+  namespace: argocd
+  labels:
+    app.kubernetes.io/name: tekton-pipelines
+    app.kubernetes.io/part-of: homelab-infra
+spec:
+  project: default
+  
+  source:
+    repoURL: https://github.com/tektoncd/pipeline.git
+    targetRevision: main
+    path: config/release
+  
+  destination:
+    server: https://kubernetes.default.svc
+    namespace: tekton-pipelines
+  
+  syncPolicy:
+    automated:
+      prune: true
+      selfHeal: true
+    syncOptions:
+    - CreateNamespace=true
+    - Validate=false
+    - RespectIgnoreDifferences=true
+    retry:
+      limit: 5
+      backoff:
+        duration: 5s
+        factor: 2
+        maxDuration: 3m
+  
+  ignoreDifferences:
+  # Ignore webhook certificate changes
+  - group: admissionregistration.k8s.io
+    kind: ValidatingWebhookConfiguration
+    jsonPointers:
+    - /webhooks/0/clientConfig/caBundle
+  - group: admissionregistration.k8s.io
+    kind: MutatingWebhookConfiguration
+    jsonPointers:
+    - /webhooks/0/clientConfig/caBundle