refactor: use ubuntu-latest runner for better compatibility

.gitea/workflows/syntax-check.yml

@@ -19,7 +19,7 @@ on:
 
 jobs:
   syntax-check:
-    runs-on: linux,x86_64,docker
+    runs-on: ubuntu-latest
     steps:
       - name: Checkout code
         run: |
@@ -31,11 +31,7 @@ jobs:
       - name: Install shellcheck
         run: |
           echo "Installing shellcheck..."
-          if command -v apk >/dev/null 2>&1; then
+          sudo apt-get update && sudo apt-get install -y shellcheck
-            apk add --no-cache shellcheck
-          elif command -v apt-get >/dev/null 2>&1; then
-            apt-get update && apt-get install -y shellcheck
-          fi
           echo "✓ shellcheck installed"
 
       - name: Run bash syntax check