ci: skip pipeline when only non-build files change

Add workflow rules to skip GitLab CI when commits only modify files
that don't affect the build or tests:
- renovate.json (Renovate bot config)
- README.md (documentation)
- LICENSE (license file)
- .tekton/* (Konflux pipelines, tested separately)

This avoids wasting CI resources on changes that don't need validation.

.gitlab-ci.yml

@@ -1,4 +1,15 @@
 ---
+workflow:
+  rules:
+    # Skip CI if only non-build files changed
+    - changes:
+        - renovate.json
+        - README.md
+        - LICENSE
+        - .tekton/*
+      when: never
+    - when: always
+
 stages:
   - build