fix(build): switch to container for build jobs

Replaces `runs-on` with `container` to utilize a Docker container
for node:20-bookworm. This enhances consistency and reproducibility
by standardizing the build environment across different runs.

.forgejo/workflows/build.yml

@@ -7,7 +7,7 @@ on:
 
 jobs:
   build:
-    runs-on: node:20-bookworm
+    container: node:20-bookworm
 
     steps:
       - name: Checkout repository