Move starter Pokemon to dedicated route that appears first

Starters are now their own "Starter" route entry instead of being
merged into the location where you receive them (Pallet Town, New Bark
Town, Route 101). This makes them always appear first in the route
list for each game.

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

backend/src/app/seeds/data/alpha-sapphire.json

@@ -1,6 +1,6 @@
 [
   {
-    "name": "Route 101",
+    "name": "Starter",
     "order": 1,
     "encounters": [
       {