fix(ci): use correct Forgejo runner label (docker)

The CI was stuck because 'runs-on: ubuntu-latest' doesn't match
any configured Forgejo runner labels.

Forgejo uses 'docker' as the default label for runners that support
containerized jobs. This matches the original workflow configuration
and should be picked up by your Forgejo runner.

.forgejo/workflows/lint-and-build.yml

@@ -17,7 +17,7 @@ env:
 jobs:
   lint:
     name: Lint
-    runs-on: ubuntu-latest
+    runs-on: docker
     container:
       image: rust:latest
     steps:
@@ -40,7 +40,7 @@ jobs:
 
   build:
     name: Build
-    runs-on: ubuntu-latest
+    runs-on: docker
     container:
       image: rust:latest
     needs: lint
@@ -64,7 +64,7 @@ jobs:
 
   docker-build:
     name: Docker Build
-    runs-on: ubuntu-latest
+    runs-on: docker
     container:
       image: docker:latest
     needs: build