feat(backend): module scaffold, config, gin router with healthz

backend/internal/api/router_test.go

@@ -0,0 +1,24 @@
+package api
+
+import (
+	"net/http"
+	"net/http/httptest"
+	"testing"
+	"time"
+
+	"booklib/internal/config"
+)
+
+func testCfg() *config.Config {
+	return &config.Config{Addr: ":8080", JWTSecret: []byte("s3cret"), ScanInterval: time.Minute, UploadMaxMB: 200}
+}
+
+func TestHealthz(t *testing.T) {
+	r := NewRouter(testCfg())
+	req := httptest.NewRequest(http.MethodGet, "/api/healthz", nil)
+	w := httptest.NewRecorder()
+	r.ServeHTTP(w, req)
+	if w.Code != http.StatusOK {
+		t.Fatalf("healthz = %d, want 200", w.Code)
+	}
+}