config: list five local settings that custom clients could not preset

Every key rustdesk reads through `LocalConfig` was checked against the
settings lists; these were in no list, so a custom client's
`default-settings` / `override-settings` could not set them:

- allow-sync-clipboard-between-sessions (rustdesk/rustdesk#15934): the
  constant lived in rustdesk's `src/clipboard.rs`; it is defined here
  now, with the other option keys.
- printer-incomming-job-action, allow-printer-auto-print,
  printer-selected-name: the incoming-print-job policy, read in
  `client/io_loop.rs`.
- enable-check-update: listed for completeness; `check_software_update`
  returns early for custom clients, so presetting it changes nothing
  there today.

Co-Authored-By: Claude Fable 5.1 <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_01EZ49AbZJYfm8NTp5yDPMab

src/config.rs

@@ -3024,6 +3024,8 @@ pub mod keys {
     pub const OPTION_FLUTTER_PEER_CARD_UI_TYLE: &str = "peer-card-ui-type";
     pub const OPTION_FLUTTER_CURRENT_AB_NAME: &str = "current-ab-name";
     pub const OPTION_ALLOW_REMOTE_CM_MODIFICATION: &str = "allow-remote-cm-modification";
+    pub const OPTION_ALLOW_SYNC_CLIPBOARD_BETWEEN_SESSIONS: &str =
+        "allow-sync-clipboard-between-sessions";
 
     pub const OPTION_PRINTER_INCOMING_JOB_ACTION: &str = "printer-incomming-job-action";
     pub const OPTION_PRINTER_ALLOW_AUTO_PRINT: &str = "allow-printer-auto-print";
@@ -3123,6 +3125,11 @@ pub mod keys {
         OPTION_DISABLE_DISCOVERY_PANEL,
         OPTION_PRE_ELEVATE_SERVICE,
         OPTION_ALLOW_REMOTE_CM_MODIFICATION,
+        OPTION_ALLOW_SYNC_CLIPBOARD_BETWEEN_SESSIONS,
+        OPTION_ENABLE_CHECK_UPDATE,
+        OPTION_PRINTER_INCOMING_JOB_ACTION,
+        OPTION_PRINTER_ALLOW_AUTO_PRINT,
+        OPTION_PRINTER_SELECTED_NAME,
         OPTION_ALLOW_AUTO_RECORD_OUTGOING,
         OPTION_HIDE_RECORDING_BUTTON,
         OPTION_VIDEO_SAVE_DIRECTORY,