Add make check target and CI workflow (#42)

Adds a `make check` target that verifies formatting (gofmt), linting (golangci-lint), and tests (go test -race) without modifying files.

Also adds `.gitea/workflows/check.yml` CI workflow that runs on pushes and PRs to main.

`make check` passes cleanly on current main.

Co-authored-by: user <user@Mac.lan guest wan>
Co-authored-by: clawbot <clawbot@noreply.git.eeqj.de>
Co-authored-by: clawbot <clawbot@sneak.berlin>
Reviewed-on: #42
Co-authored-by: clawbot <sneak+clawbot@sneak.cloud>
Co-committed-by: clawbot <sneak+clawbot@sneak.cloud>

.gitea/workflows/check.yml

@@ -0,0 +1,14 @@
+name: check
+on:
+  push:
+    branches: [main]
+  pull_request:
+    branches: [main]
+jobs:
+  check:
+    runs-on: ubuntu-latest
+    steps:
+      # actions/checkout v4, 2024-09-16
+      - uses: actions/checkout@34e114876b0b11c390a56381ad16ebd13914f8d5
+      - name: Build and check
+        run: docker build .