fix: stabilize earth bgp geography and rendering

backend/app/core/countries.py

@@ -232,6 +232,30 @@ for canonical, aliases in COUNTRY_ENTRIES:
         COUNTRY_ALIAS_MAP[alias.casefold()] = canonical
 
 
+COUNTRY_CENTROIDS = {
+    "美国": {"latitude": 39.8283, "longitude": -98.5795},
+    "英国": {"latitude": 55.3781, "longitude": -3.4360},
+    "荷兰": {"latitude": 52.1326, "longitude": 5.2913},
+    "日本": {"latitude": 36.2048, "longitude": 138.2529},
+    "德国": {"latitude": 51.1657, "longitude": 10.4515},
+    "法国": {"latitude": 46.2276, "longitude": 2.2137},
+    "新加坡": {"latitude": 1.3521, "longitude": 103.8198},
+    "中国": {"latitude": 35.8617, "longitude": 104.1954},
+    "中国（香港）": {"latitude": 22.3193, "longitude": 114.1694},
+    "中国（台湾）": {"latitude": 23.6978, "longitude": 120.9605},
+    "韩国": {"latitude": 35.9078, "longitude": 127.7669},
+    "俄罗斯": {"latitude": 61.5240, "longitude": 105.3188},
+    "加拿大": {"latitude": 56.1304, "longitude": -106.3468},
+    "澳大利亚": {"latitude": -25.2744, "longitude": 133.7751},
+    "巴西": {"latitude": -14.2350, "longitude": -51.9253},
+    "南非": {"latitude": -30.5595, "longitude": 22.9375},
+    "西班牙": {"latitude": 40.4637, "longitude": -3.7492},
+    "意大利": {"latitude": 41.8719, "longitude": 12.5674},
+    "瑞士": {"latitude": 46.8182, "longitude": 8.2275},
+    "阿联酋": {"latitude": 23.4241, "longitude": 53.8478},
+}
+
+
 def normalize_country(value: Any) -> Optional[str]:
     if value is None:
         return None
@@ -258,6 +282,13 @@ def normalize_country(value: Any) -> Optional[str]:
     return COUNTRY_ALIAS_MAP.get(lowered)
 
 
+def get_country_centroid(value: Any) -> Optional[dict[str, float]]:
+    canonical = normalize_country(value)
+    if not canonical:
+        return None
+    return COUNTRY_CENTROIDS.get(canonical)
+
+
 def get_country_search_variants(value: Any) -> list[str]:
     canonical = normalize_country(value)
     if canonical is None: