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

.sops.yaml

@@ -2,4 +2,5 @@ creation_rules:
   # `secrets?` — singular too. A `seed-repo-secret.yaml` once slipped this regex
   # and was committed in plaintext to a public remote.
   - path_regex: k8s/.*secrets?.*\.ya?ml
+    encrypted_regex: ^(data|stringData)$
     age: age1e5fq3hwxy78psus2nfvmtmua36g0u3suk78ephw6246l974d2utsvn0hla