feat(data): expand challenge seed pool with 75 verified wins

Adds a gen_seeds binary to solitaire_assetgen that brute-searches seeds
for hands solvable in ≤250 moves, then writes the list.  The 75 new
seeds (0xCAFEBABE prefix) are appended to CHALLENGE_SEEDS in
solitaire_data::challenge.

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

Cargo.lock

@@ -6967,6 +6967,8 @@ version = "0.1.0"
 dependencies = [
  "ab_glyph",
  "png 0.17.16",
+ "solitaire_core",
+ "solitaire_data",
 ]
 
 [[package]]