Add --export flag to export all seed data from DB to JSON

Replaces --export-bosses with a unified --export that dumps games,
pokemon, evolutions, routes/encounters, and bosses to seeds/data/.
Each export function mirrors the corresponding API export endpoint.

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

backend/src/app/seeds/__main__.py

@@ -1,24 +1,24 @@
 """Entry point for running seeds.
 
 Usage:
-    python -m app.seeds                  # Run seed
-    python -m app.seeds --verify         # Run seed + verification
-    python -m app.seeds --export-bosses  # Export boss data to seed JSON files
+    python -m app.seeds            # Run seed
+    python -m app.seeds --verify   # Run seed + verification
+    python -m app.seeds --export   # Export all seed data from DB to JSON files
 """
 
 import asyncio
 import sys
 
 from app.core.database import engine
-from app.seeds.run import export_bosses, seed, verify
+from app.seeds.run import export_all, seed, verify
 
 
 async def main():
     verbose = "--verbose" in sys.argv or "-v" in sys.argv
     engine.echo = verbose
 
-    if "--export-bosses" in sys.argv:
-        await export_bosses()
+    if "--export" in sys.argv:
+        await export_all()
         return
 
     await seed()