ci: add Gitea Actions workflow with gofmt and test jobs

Add CI workflow at .gitea/workflows/ci.yml triggered on pull_request
with two jobs: fmt (gofmt check) and test (go test ./...).

Fix gofmt issues (import ordering) in 7 files so CI passes from
the start.

Fixes #7

Co-Authored-By: Claude Opus 4.7 <noreply@anthropic.com>

.gitea/workflows/ci.yml

@@ -0,0 +1,29 @@
+name: CI
+
+on:
+  pull_request:
+
+jobs:
+  fmt:
+    runs-on: ubuntu-latest
+    steps:
+      - uses: actions/checkout@v4
+      - uses: actions/setup-go@v5
+        with:
+          go-version-file: go.mod
+      - run: |
+          out=$(gofmt -l .)
+          if [ -n "$out" ]; then
+            echo "Files not formatted:"
+            echo "$out"
+            exit 1
+          fi
+
+  test:
+    runs-on: ubuntu-latest
+    steps:
+      - uses: actions/checkout@v4
+      - uses: actions/setup-go@v5
+        with:
+          go-version-file: go.mod
+      - run: go test ./...