optimize first-user check in create_profile to avoid full table scan

[ilikeworking2005]

Problem:
create_profile determines if a user is the first registrant by fetching every user from the database and checking len(existing) == 0. As the userbase grows this instantiates unnecessary ORM objects for every row wasting memory and database I/O.

Fix
Replace the full fetch with a LIMIT 1 query on User.id only the database stops after finding a single row making this effectively O(1) regardless of table size.

Before

result = await db.execute(select(User))
existing = result.scalars().all()
is_first_user = len(existing) == 0

After

result = await db.execute(select(User.id).limit(1))
is_first_user = result.scalar_one_or_none() is None
Impact