Feat: Sub-license count limit - LicenseLimit field in licenses.ini + context menu

- Add LicenseLimit field to LicenseInfo struct (0 = not set, unlimited)
- Add GetLicenseLimit/SetLicenseLimit: read/write LicenseLimit key in licenses.ini
- Append |lic:N to reserved field in TOKEN_AUTH response only when
  LicenseLimit > 0; absent |lic: means no limit (client defaults to 9999),
  so super admin authenticating to its own server is never falsely terminated
- Add "Sub-license limit" item in CLicenseDlg right-click menu (1-9999,
  empty = clear limit); menu label shows current value in real time
- Limit change takes effect when sub-client re-authenticates

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

server/2015Remote/lang/en_US.ini

@@ -1935,3 +1935,11 @@ FRPC Զ
 [安全提示] 请设置Web访问密码!!!=[Security Warning] Please set web password!!!
 查看=View Window
 该窗口已最小化，请先还原后再查看。=The window is minimized. Please restore it before viewing.
+下级数量限制: %d (&L)...=License Limit: %d (&L)...
+下级数量限制 (&L)...=License Limit (&L)...
+下级数量限制 (%s)=License Limit (%s)
+数量上限(1-9999):=Limit(1-9999):
+请输入 1 到 9999 之间的整数。=Please input a integer range 1, 9999.
+输入无效=Invalid Input
+授权 %s 的下级数量上限已设置为 %d。\n下级重新认证后生效。=Sub-license limit for %s has been set to %d.\nTakes effect when the sub-client re-authenticates.
+授权 %s 的下级数量限制已清除。\n下级重新认证后生效。=Sub-license limit for %s has been cleared.\nTakes effect when the sub-client re-authenticates.