chore: add updater image configuration to Docker workflow

- Introduced a new job for building and pushing an updater Docker image, dynamically setting its name based on the repository structure.
- Updated existing image name configurations for frontend and backend to strip version numbers, ensuring cleaner image tags.
- Enhanced the Docker workflow with steps for checking out the repository, configuring Buildx, and logging into the Gitea registry.

deploy/updater/targets.json.example

@@ -0,0 +1,24 @@
+{
+  "targets": [
+    {
+      "id": "backend",
+      "container_name": "mmapp-backend",
+      "image": "git.shts.su/denozord/mikrotikmanager-backend:latest",
+      "health": {
+        "type": "http",
+        "url": "http://127.0.0.1:8000/health",
+        "expect_status": 200
+      }
+    },
+    {
+      "id": "frontend",
+      "container_name": "mmapp-frontend",
+      "image": "git.shts.su/denozord/mikrotikmanager-frontend:latest",
+      "health": {
+        "type": "http",
+        "url": "http://127.0.0.1:3000/",
+        "expect_status": 200
+      }
+    }
+  ]
+}