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/ui_interface.rs

@@ -1444,3 +1444,22 @@ pub fn check_hwcodec() {
         })
     }
 }
+
+#[cfg(feature = "flutter")]
+pub fn get_unlock_pin() -> String {
+    #[cfg(any(target_os = "android", target_os = "ios"))]
+    return String::default();
+    #[cfg(not(any(target_os = "android", target_os = "ios")))]
+    return ipc::get_unlock_pin();
+}
+
+#[cfg(feature = "flutter")]
+pub fn set_unlock_pin(pin: String) -> String {
+    #[cfg(any(target_os = "android", target_os = "ios"))]
+    return String::default();
+    #[cfg(not(any(target_os = "android", target_os = "ios")))]
+    match ipc::set_unlock_pin(pin, true) {
+        Ok(_) => String::default(),
+        Err(err) => err.to_string(),
+    }
+}