feat(admin): city delete with impact preview; optional partner fields

Allow deleting open cities after listing partners/stores; company name, address, and districts optional on partner create.

Co-authored-by: Cursor <cursoragent@cursor.com>

packages/domain/src/city-partner.ts

@@ -95,12 +95,7 @@ export function validatePartnerCityBinding(
     return { ok: true };
   }
 
-  const districts = normalizeDistrictCodes(input.districtCodes);
-  if (!districts.length) {
-    return { ok: false, message: '区域合伙人须至少选择一个区县' };
-  }
-
-  // 区县仅为标识，允许多个区域合伙人选择相同区县
+  // 区域合伙人所选区县可为空（录入时可稍后补全）
   return { ok: true };
 }