ci: Disable Go cache to prevent hanging on Gitea runners

The actions/setup-go@v5 cache feature tries to upload to GitHub's
cache infrastructure, which doesn't exist on self-hosted Gitea
runners. This causes jobs to hang indefinitely during the post step.

🤖 Generated with [Claude Code](https://claude.com/claude-code)

Co-Authored-By: Claude Opus 4.5 <noreply@anthropic.com>

.gitea/workflows/ci.yml

@@ -15,6 +15,7 @@ jobs:
       - uses: actions/setup-go@v5
         with:
           go-version: '1.21'
+          cache: false
 
       - name: Build
         run: go build ./...

.gitea/workflows/release.yml

@@ -14,6 +14,7 @@ jobs:
       - uses: actions/setup-go@v5
         with:
           go-version: '1.21'
+          cache: false
 
       - name: Build
         run: go build ./...