Immich theming: Overpass font, anti-aliased white icon

- all text renders in the bundled Overpass SemiBold (Immich's
  typeface) via vita2d's FreeType path, with a per-pixel-size font
  instance cache (vita2d's glyph atlas caches glyphs at their first
  drawn size, which rendered stray oversized letters when sizes mixed)
  and a system-PGF fallback if the TTF fails to load; the OFL license
  ships in the vpk next to the font
- freetype's bzip2 references get failing stubs (the SDK ships no
  libbz2 and plain TTFs never hit that path)
- icon rebuilt from the official high-res Immich logo: anti-aliased,
  flattened onto white so the LiveArea no longer shows it on black

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

CMakeLists.txt

@@ -53,4 +53,6 @@ vita_create_vpk(${PROJECT_NAME}.vpk ${VITA_TITLEID} ${PROJECT_NAME}.self
   VERSION ${VITA_VERSION}
   NAME ${VITA_APP_NAME}
   FILE ${CMAKE_SOURCE_DIR}/assets/sce_sys/icon0.png sce_sys/icon0.png
+  FILE ${CMAKE_SOURCE_DIR}/assets/Overpass-SemiBold.ttf font.ttf
+  FILE ${CMAKE_SOURCE_DIR}/assets/OFL-Overpass.txt OFL-Overpass.txt
 )