Fix: Add missing FileManagerDlg translations to language files

FileManagerDlg.cpp still had several user-facing Chinese strings with no
entry in en_US/zh_TW/de_DE: the "invalid file handle", "no files
selected", "V2 transfer started", "V2 download request sent" and "main
connection not found" messages. Add translations for all five.

The "main connection not found" string contained a literal '=', which
CIniParser treats as the key/value delimiter, so it could never match as
a translation key. Reword it to "clientID %llu" (no '=') so the key
round-trips. The two Mprintf log lines on the V2 checksum path are
log-only and intentionally left untranslated.

Co-Authored-By: deepseek-v4-pro

server/2015Remote/lang/zh_TW.ini

@@ -2098,3 +2098,8 @@ TLS
 已将 %d 个 IP 加入白名单=已將 %d 個 IP 加入白名單
 %d 个 IP 已在白名单中=%d 個 IP 已在白名單中
 %d 个 IP 已封禁，无法加入白名单=%d 個 IP 已封禁，無法加入白名單
+%s 文件句柄无效=%s 檔案控制代碼無效
+没有选中任何文件=沒有選取任何檔案
+V2传输已启动，共 %d 个文件 -> %s=V2 傳輸已啟動，共 %d 個檔案 -> %s
+V2下载请求已发送，共 %d 个项目=V2 下載請求已傳送，共 %d 個項目
+找不到主连接: clientID %llu=找不到主連線: clientID=%llu