chore: post-sync cleanup and clang-format

- Remove stale Lyra3CoversTheme.h (functionality merged into LyraTheme)
- Fix UITheme.cpp to use LyraTheme for LYRA_3_COVERS theme variant
- Update open-x4-sdk submodule to 91e7e2b (drawImageTransparent support)
- Run clang-format on all source files

Co-authored-by: Cursor <cursoragent@cursor.com>

src/activities/home/HomeActivity.cpp

@@ -5,8 +5,8 @@
 #include <GfxRenderer.h>
 #include <HalStorage.h>
 #include <I18n.h>
-#include <Utf8.h>
 #include <PlaceholderCoverGenerator.h>
+#include <Utf8.h>
 #include <Xtc.h>
 
 #include <cstdio>