unlock with PIN (#8977)

* add custom password to unlock settings

* If not set, use admin password; if set, use custom settings password.
* At least 4 characters.
* Set with gui or command line.

Signed-off-by: 21pages <sunboeasy@gmail.com>

* Update cn.rs

---------

Signed-off-by: 21pages <sunboeasy@gmail.com>
Co-authored-by: RustDesk <71636191+rustdesk@users.noreply.github.com>

src/lang/cn.rs

@@ -632,5 +632,9 @@ pub static ref T: std::collections::HashMap<&'static str, &'static str> =
         ("About RustDesk", "关于 RustDesk"),
         ("Send clipboard keystrokes", "发送剪贴板按键"),
         ("network_error_tip", "请检查网络连接，然后点击再试"),
+        ("Unlock with PIN", "使用 PIN 码解锁设置"),
+        ("Requires at least {} characters", "不少于{}个字符"),
+        ("Wrong PIN", "PIN 码错误"),
+        ("Set PIN", "设置 PIN 码"),
     ].iter().cloned().collect();
 }