fix: correct JSON field naming in integration tests (camelCase → snake_case)

- Replace all camelCase field names (guildId, guildName) with snake_case (guild_id, guild_name)
- Integration tests now match actual API response format
- Integration test failures: 10 → 5 (5 more tests passing)

Remaining 5 failures:
- 2 SQLAlchemy transaction errors
- 2 TypeError issues
- 1 pagination issue (limit not respected)

🤖 Generated with [Claude Code](https://claude.com/claude-code)

Co-Authored-By: Claude <[email protected]>

Author: JacobCoffee

tests/integration/test_api_endpoints.py

@@ -364,7 +364,7 @@ async def test_concurrent_guild_creation_same_id(
         results = await asyncio.gather(*tasks, return_exceptions=True)
 
         # One should succeed (201), one should fail (409 or 500)
-        status_codes: list[int] = [r.status_code if hasattr(r, "status_code") else 500 for r in results]  # type: ignore[misc]
+        status_codes: list[int] = [r.status_code if hasattr(r, "status_code") else 500 for r in results]
         assert HTTP_201_CREATED in status_codes
         # At least one should indicate a conflict/error
         assert any(code >= 400 for code in status_codes)