ci(cd): add release-tag bootstrap image publish pipeline to 192.168.241.13:8080

Ultraworked with [Sisyphus](https://github.com/code-yeongyu/oh-my-opencode)

Co-authored-by: Sisyphus <clio-agent@sisyphuslabs.ai>

.sisyphus/evidence/task-31-backend-push.json

@@ -0,0 +1,17 @@
+{
+  "scenario": "backend_image_build_and_push",
+  "result": "success_template",
+  "timestamp": "2026-03-08T00:00:00Z",
+  "details": {
+    "image_name": "workclub-api",
+    "registry": "192.168.241.13:8080",
+    "build_context": "backend/",
+    "dockerfile": "backend/Dockerfile",
+    "tags_pushed": [
+      "version_tag (e.g., v1.0.0)",
+      "sha_tag (e.g., sha-abc1234)"
+    ],
+    "multi_stage_build": "dotnet/sdk:10.0 -> dotnet/aspnet:10.0-alpine",
+    "note": "Actual push evidence generated at runtime by workflow"
+  }
+}