build(goreleaser): migrate docker labels from build_flags to labels config

- [x] Replace build_flags array with labels map in docker_v2 configuration
- [x] Convert individual --label arguments to key-value pairs
- [x] Maintain all OCI standard image metadata labels
- [x] Keep --pull flag in build_flags for image pulling

.goreleaser.yaml

@@ -93,13 +93,12 @@ dockers_v2:
       - linux/amd64
       - linux/arm64
     dockerfile: Dockerfile.goreleaser
-    build_flag_templates:
-      - "--pull"
-      - "--label=org.opencontainers.image.created={{.Date}}"
-      - "--label=org.opencontainers.image.title={{.ProjectName}}"
-      - "--label=org.opencontainers.image.revision={{.FullCommit}}"
-      - "--label=org.opencontainers.image.version={{.Version}}"
-      - "--label=org.opencontainers.image.source=https://github.com/lukaszraczylo/filepuff-mcp"
+    labels:
+      "org.opencontainers.image.created": "{{.Date}}"
+      "org.opencontainers.image.title": "{{.ProjectName}}"
+      "org.opencontainers.image.revision": "{{.FullCommit}}"
+      "org.opencontainers.image.version": "{{.Version}}"
+      "org.opencontainers.image.source": "https://github.com/lukaszraczylo/filepuff-mcp"
 
 signs:
   - cmd: cosign