Add game data seeding from PokeAPI with level ranges

Seed the database with Pokemon game data for 5 games (FireRed, LeafGreen,
Emerald, HeartGold, SoulSilver) using pokebase. Includes Alembic migrations
for route unique constraints and encounter level ranges, a two-phase seed
system (offline fetch to JSON, then idempotent upserts), and Dockerfile
updates for the seed runner.

Co-Authored-By: Claude Opus 4.5 <noreply@anthropic.com>

backend/src/app/seeds/__main__.py

@@ -0,0 +1,21 @@
+"""Entry point for running seeds.
+
+Usage:
+    python -m app.seeds           # Run seed
+    python -m app.seeds --verify  # Run seed + verification
+"""
+
+import asyncio
+import sys
+
+from app.seeds.run import seed, verify
+
+
+async def main():
+    await seed()
+    if "--verify" in sys.argv:
+        await verify()
+
+
+if __name__ == "__main__":
+    asyncio.run(main())