Use docker-tags plugin for flexible image tagging

Add generate-tags step with branch, sha, edge, build number, and
semver tag formats. Enable tag events for release workflows.

.woodpecker.yaml

@@ -1,16 +1,25 @@
 when:
-  - event: [push, pull_request, manual]
+  - event: [push, pull_request, manual, tag]
 
 steps:
+  - name: generate-tags
+    image: ghcr.io/abh/woodpecker-docker-tags-plugin:sha-86e52ce
+    settings:
+      tags: |
+        branch
+        sha
+        edge
+        raw -v build-${CI_PIPELINE_NUMBER}
+        semver --format {{major}}
+        semver --format {{major}}.{{minor}}
+        semver --format {{major}}.{{minor}}.{{patch}}
+
   - name: docker
     image: woodpeckerci/plugin-kaniko
     settings:
       dockerfile: Dockerfile
       registry: harbor.ntppool.org
       repo: library/static-web
-      tags:
-        - ${CI_COMMIT_SHA:0:7}
-        - ${CI_COMMIT_BRANCH}
       cache: true
       username:
         from_secret: harbor_library_username