fix(geo): 修复香港等节点地图质心缺失落到南美占位

补全 Hong Kong/Singapore/Taiwan 质心数据，并改进复合地名与 ISO 匹配，
避免 geo 无精确经纬度时错误回退到巴西等地的占位坐标。

pkg/geoip/country_centroid_test.go

@@ -11,3 +11,34 @@ func TestCountryCentroidGermany(t *testing.T) {
 		t.Fatalf("unexpected Germany centroid: %f,%f", lat, lon)
 	}
 }
+
+func TestCountryCentroidHongKongSingaporeTaiwan(t *testing.T) {
+	cases := []struct {
+		iso      string
+		name     string
+		minLat   float64
+		maxLat   float64
+		minLon   float64
+		maxLon   float64
+	}{
+		{iso: "HK", name: "Hong Kong", minLat: 22, maxLat: 23, minLon: 113, maxLon: 115},
+		{iso: "SG", name: "Singapore", minLat: 1, maxLat: 2, minLon: 103, maxLon: 104},
+		{iso: "TW", name: "Taiwan", minLat: 22, maxLat: 26, minLon: 119, maxLon: 122},
+	}
+	for _, tc := range cases {
+		lat, lon, ok := CountryCentroidByISO(tc.iso)
+		if !ok {
+			t.Fatalf("expected %s centroid by ISO", tc.iso)
+		}
+		if lat < tc.minLat || lat > tc.maxLat || lon < tc.minLon || lon > tc.maxLon {
+			t.Fatalf("%s ISO centroid out of range: %f,%f", tc.iso, lat, lon)
+		}
+		lat, lon, ok = CountryCentroidByName(tc.name)
+		if !ok {
+			t.Fatalf("expected %s centroid by name", tc.name)
+		}
+		if lat < tc.minLat || lat > tc.maxLat || lon < tc.minLon || lon > tc.maxLon {
+			t.Fatalf("%s name centroid out of range: %f,%f", tc.name, lat, lon)
+		}
+	}
+}