Add game category and region metadata for genlocke presets

Add `category` field (original/remake/enhanced/sequel/spinoff) to the
Game model and tag all 38 games. Create regions.json with generation
mapping, ordering, and genlocke preset defaults per region. Add
GET /games/by-region endpoint returning games grouped by region.

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

backend/src/app/models/game.py

@@ -12,6 +12,7 @@ class Game(Base):
     slug: Mapped[str] = mapped_column(String(100), unique=True)
     generation: Mapped[int] = mapped_column(SmallInteger)
     region: Mapped[str] = mapped_column(String(50))
+    category: Mapped[str | None] = mapped_column(String(20))  # original, remake, enhanced, sequel, spinoff
     box_art_url: Mapped[str | None] = mapped_column(String(500))
     release_year: Mapped[int | None] = mapped_column(SmallInteger)
     color: Mapped[str | None] = mapped_column(String(7))  # Hex color e.g. #FF0000