fix: align CustomCommandCreator.discord_id model with BIGINT column (#78)

Closes #78

Change CharField(max_length=20) to BigIntegerField to match the BIGINT
column created by the migration. Remove the str() workaround in
get_creator_by_discord_id() that was compensating for the type mismatch.

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

app/db_engine.py

@@ -2224,7 +2224,7 @@ class Decision(BaseModel):
 
 class CustomCommandCreator(BaseModel):
     """Model for custom command creators."""
-    discord_id = CharField(max_length=20, unique=True)  # Discord snowflake ID as string
+    discord_id = BigIntegerField(unique=True)
     username = CharField(max_length=32)
     display_name = CharField(max_length=32, null=True)
     created_at = DateTimeField()

app/routers_v3/custom_commands.py

@@ -175,7 +175,7 @@ def delete_custom_command(command_id: int):
 def get_creator_by_discord_id(discord_id: int):
     """Get a creator by Discord ID"""
     creator = CustomCommandCreator.get_or_none(
-        CustomCommandCreator.discord_id == str(discord_id)
+        CustomCommandCreator.discord_id == discord_id
     )
     if creator:
         return model_to_dict(creator)