fix: remove redundant unique constraints on id columns from all migrations

Remove UniqueConstraint('id') from all create_table calls in the initial
migration (40 occurrences) and the bulk constraint additions from the
superadmin migration (43 create + 43 drop). These were redundant with
PrimaryKeyConstraint('id') which already guarantees uniqueness.

Also removes duplicate unique enforcement on superadmins.email and
superadmin_sessions.token (kept the unique indexes, dropped the
table-level UniqueConstraints).

Fixes the root cause in BaseModel by removing unique=True from the id
column definition, which was causing Alembic autogenerate to produce
these redundant constraints.

Renames idx_cert_audit_org to ix_certificate_audit_logs_organization_id
to follow Alembic naming conventions.

gatehouse_app/models/base.py

@@ -13,7 +13,6 @@ class BaseModel(db.Model):
         db.String(36),
         primary_key=True,
         default=lambda: str(uuid.uuid4()),
-        unique=True,
         nullable=False,
     )
     created_at = db.Column(db.DateTime, nullable=False, default=lambda: datetime.now(timezone.utc))