ci: add Gitea Actions workflow for make check (closes #96)

Adds .gitea/workflows/check.yml — runs make check on pushes to main
and PRs targeting main.

Uses golangci-lint v2.10.1 (pinned) matching the repo's v2 config.
Only adds the workflow file. No other files modified.

.gitea/workflows/check.yml

@@ -17,7 +17,7 @@ jobs:
           go-version-file: go.mod
 
       - name: Install golangci-lint
-        run: go install github.com/golangci/golangci-lint/v2/cmd/golangci-lint@latest
+        run: go install github.com/golangci/golangci-lint/v2/cmd/golangci-lint@v2.10.1
 
       - name: Install goimports
         run: go install golang.org/x/tools/cmd/goimports@latest