Add alternative 'z' keybinding for menu (workaround for UOSC claiming right-click)

Due to UOSC loading after input.conf with force flags, it claims mbtn_right globally.
Added 'z' key as alternative menu trigger that UOSC doesn't control.
Also kept 'm' key binding as primary menu trigger.
input.conf still attempts mbtn_right routing but UOSC overrides it.

Test with: Press 'm' or 'z' to open menu

MPV/LUA/main.lua

@@ -2903,6 +2903,11 @@ mp.add_key_binding("m", "medios-menu", function()
     M.show_menu()
 end)
 
+mp.add_key_binding("z", "medios-menu-alt", function()
+    _lua_log('[KEY] z pressed (alternative menu trigger)')
+    M.show_menu()
+end)
+
 -- NOTE: mbtn_right is claimed by UOSC globally, so we can't override it here.
 -- Instead, use script-message handler below for alternative routing.
 mp.add_key_binding("ctrl+i", "medios-info", M.get_file_info)