Fix: Decode geographic location as UTF-8 across client and server

Geographic location (city, country) from the geo APIs is UTF-8, but the client
and several server paths converted or stored it in the system ANSI code page,
turning umlauts ("ö"/"ä") into "?" or GBK mojibake ("B枚blingen"). Keep the
value UTF-8 end to end: the client caches it as UTF-8 and re-queries once after
an upgrade (keyed by __DATE__, the app's version convention), while the server
stores and displays it as UTF-8 in the online list, the activity log, the
client-info export, JSON/email payloads and search.

Also add a confirmation prompt before opening a remote chat from the toolbar,
with German, English and Traditional-Chinese translations.

Co-Authored-By: deepseek-v4-pro

common/location.h

@@ -328,8 +328,10 @@ private:
             }
         }
 
-        std::string city = Utf8ToAnsi(json[cityField].asString());
-        std::string country = Utf8ToAnsi(json[countryField].asString());
+        // 地理位置 API 返回 UTF-8；不再转 CP_ACP——那会把 ö/ä/ß 等变音符替换成 '?'。
+        // GetGeoLocation 现统一返回 UTF-8，消费方按需用 NormalizeLocationToUtf8 / SafeUtf8ToAnsi 转。
+        std::string city = json[cityField].asString();
+        std::string country = json[countryField].asString();
 
         if (!city.empty() && !country.empty()) return city + ", " + country;
         if (!city.empty()) return city;