i18n(ru): translate untranslated PreSharedKey label and Export menu (#9309)

Two strings in ResUI.ru.resx were left with their English (or identifier) values and surfaced as untranslated text on a Russian UI culture. This commit translates both, keeping the existing translation style and the existing technical vocabulary established earlier in this file.

Changes:

1. TbPreSharedKey: 'PreSharedKey' -> 'Общий ключ (PSK)'

   The label is the WireGuard pre-shared-key field. The sibling WireGuard fields are already translated in the same file (TbPublicKey -> 'Открытый ключ', TbPrivateKey -> 'Приватный ключ'), so leaving this one as the raw identifier was inconsistent. 'Общий ключ' matches the wording used in Russian-localized network UIs for this concept (NetworkManager, MikroTik, OpenVPN GUIs); the '(PSK)' suffix preserves the technical abbreviation so users familiar with the WireGuard documentation immediately recognize the field.

2. menuExport2InnerUri: 'Export v2rayN Internal Share Link to Clipboard' -> 'Экспорт внутренней ссылки v2rayN в буфер обмена'

   This context-menu item was added recently and the Russian resource kept the English string verbatim. The translation follows the convention of the sibling export-to-clipboard items (menuExport2ShareUrlBase64 uses 'Экспорт ... в буфер обмена'), and 'внутренней ссылки v2rayN' preserves the 'internal' qualifier because this share-link format is specific to v2rayN's own importer and not interchangeable with the standard VMess/VLESS/Trojan/etc. URI schemes.

Verified:

- Diff scope: only ResUI.ru.resx, only the two <value> elements; the .resx XML schema headers and all other keys are untouched.

- Full audit of ResUI.ru.resx vs ResUI.resx: every other key is present and translated; these were the only two strings still surfacing in English on a Russian UI culture.

- 'dotnet build v2rayN/v2rayN.sln -c Release' passes with 0 errors and 0 warnings.

v2rayN/ServiceLib/Resx/ResUI.ru.resx

@@ -1726,9 +1726,9 @@
     <value>Для среды с несколькими сетевыми интерфейсами укажите имя интерфейса для привязки. Работает только в Windows и режиме TUN</value>
   </data>
   <data name="TbPreSharedKey" xml:space="preserve">
-    <value>PreSharedKey</value>
+    <value>Общий ключ (PSK)</value>
   </data>
   <data name="menuExport2InnerUri" xml:space="preserve">
-    <value>Export v2rayN Internal Share Link to Clipboard</value>
+    <value>Экспорт внутренней ссылки v2rayN в буфер обмена</value>
   </data>
 </root>