Refactor geo re-resolve endpoint into geo_service and add typed response

backend/app/models/geo.py

@@ -57,6 +57,19 @@ class GeoCacheStatsResponse(BaseModel):
     dirty_size: int = Field(..., description="Number of newly resolved entries not yet flushed to disk.")
 
 
+class GeoReResolveResponse(BaseModel):
+    """Response for ``POST /api/geo/re-resolve``.
+
+    Reports how many previously unresolved IPs were retried and how many
+    gained a resolved country code after the re-resolve operation.
+    """
+
+    model_config = ConfigDict(strict=True)
+
+    resolved: int = Field(..., description="Number of IPs successfully resolved.")
+    total: int = Field(..., description="Number of IPs retried.")
+
+
 class IpLookupResponse(BaseModel):
     """Response for ``GET /api/geo/lookup/{ip}``.