fix: CI increase timeout, cleared stale git lock on runner

Stale shallow.lock was blocking checkout. Removed it on the runner.

Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>

.gitea/workflows/build-iso.yml

@@ -8,7 +8,7 @@ on:
 jobs:
   build-iso:
     runs-on: ubuntu-latest
-    timeout-minutes: 30
+    timeout-minutes: 45
     steps:
       - name: Checkout
         uses: actions/checkout@v4