chore: merge backend repo history into monorepo at backend/

git-subtree-dir: backend
git-subtree-mainline: dc11190527
git-subtree-split: acae976622

backend/internal/utils/geo_test.go

@@ -0,0 +1,18 @@
+package utils
+
+import "testing"
+
+func TestHaversineKM_SamePoint(t *testing.T) {
+	d := HaversineKM(35.6892, 51.3890, 35.6892, 51.3890)
+	if d > 0.001 {
+		t.Fatalf("expected ~0km for identical points, got %v", d)
+	}
+}
+
+func TestHaversineKM_TehranToIsfahan(t *testing.T) {
+	// فاصله‌ی تهران تا اصفهان تقریباً ۳۴۰ کیلومتره (خط مستقیم)
+	d := HaversineKM(35.6892, 51.3890, 32.6546, 51.6680)
+	if d < 300 || d > 380 {
+		t.Fatalf("expected ~340km between Tehran and Isfahan, got %v", d)
+	}
+}