Strip legacy save/settings systems for a unified savemanager rewrite; split uielement list out of uielement.c

Removes the per-platform save/savestream/autosave implementations, the settings UI frames, and the autosave overlay, replacing them with a savemanager.c/h + savefile.h/savedevice.h scaffold to build the new save system on top of. Also separates the concrete UI_ELEMENTS registration into uielementlist.h/.c so uielement.c only holds the generic per-element lifecycle logic.

Co-Authored-By: Claude Sonnet 5 <noreply@anthropic.com>

src/dusklinux/input/inputlinux.c

@@ -6,7 +6,6 @@
  */
 
 #include "input/input.h"
-#include "save/save.h"
 
 inputbuttondata_t INPUT_BUTTON_DATA[] = {
   #ifdef DUSK_INPUT_GAMEPAD
@@ -548,5 +547,5 @@ errorret_t inputInitLinux(void) {
 }
 
 float_t inputGetDeadzoneSDL2(const inputbutton_t button) {
-  return saveGetMeta()->deadzone;
+  return 0.2f;
 }