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/seeds/data/regions.json

@@ -0,0 +1,83 @@
+[
+  {
+    "name": "kanto",
+    "generation": 1,
+    "order": 1,
+    "genlocke_defaults": {
+      "true": "red",
+      "normal": "firered"
+    }
+  },
+  {
+    "name": "johto",
+    "generation": 2,
+    "order": 2,
+    "genlocke_defaults": {
+      "true": "gold",
+      "normal": "heartgold"
+    }
+  },
+  {
+    "name": "hoenn",
+    "generation": 3,
+    "order": 3,
+    "genlocke_defaults": {
+      "true": "ruby",
+      "normal": "alpha-sapphire"
+    }
+  },
+  {
+    "name": "sinnoh",
+    "generation": 4,
+    "order": 4,
+    "genlocke_defaults": {
+      "true": "diamond",
+      "normal": "platinum"
+    }
+  },
+  {
+    "name": "unova",
+    "generation": 5,
+    "order": 5,
+    "genlocke_defaults": {
+      "true": "black",
+      "normal": "black"
+    }
+  },
+  {
+    "name": "kalos",
+    "generation": 6,
+    "order": 6,
+    "genlocke_defaults": {
+      "true": "x",
+      "normal": "x"
+    }
+  },
+  {
+    "name": "alola",
+    "generation": 7,
+    "order": 7,
+    "genlocke_defaults": {
+      "true": "sun",
+      "normal": "ultra-sun"
+    }
+  },
+  {
+    "name": "galar",
+    "generation": 8,
+    "order": 8,
+    "genlocke_defaults": {
+      "true": "sword",
+      "normal": "sword"
+    }
+  },
+  {
+    "name": "paldea",
+    "generation": 9,
+    "order": 9,
+    "genlocke_defaults": {
+      "true": "scarlet",
+      "normal": "scarlet"
+    }
+  }
+]