feat(engine,assetgen): generate 52 individual card face PNGs

Replace the single shared face.png placeholder with 52 individual card
face images (120×168 px each), generated by the updated gen_art tool:

- solitaire_assetgen: add ab_glyph dep; rewrite gen_art to render each
  card with FiraMono rank characters, programmatic suit symbols (heart,
  spade, diamond, club drawn via circles/triangles), and standard pip
  layout for numbered cards (A–10) plus large face letter for J/Q/K.
- CardImageSet: replace single `face` handle with `faces: [[Handle; 13]; 4]`
  indexed by [suit][rank].
- card_sprite(): select the per-card face image by suit/rank indices.
- spawn/update_card_entity: suppress Text2d overlay when PNG faces are
  loaded (rank/suit baked into image); keep overlay in solid-colour
  fallback for tests.
- gen_sfx.rs: rename `gen` variable to `make` (reserved keyword in 2024).

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

Cargo.lock

@@ -7514,6 +7514,7 @@ dependencies = [
 name = "solitaire_assetgen"
 version = "0.1.0"
 dependencies = [
+ "ab_glyph",
  "png 0.17.16",
 ]