chore: merge main into branch, resolve conflict in models.py

Both sets of UserProfile columns are retained:
- is_complimentary (from main, migration 019_add_is_complimentary)
- subscription_change_pending_tier / subscription_change_pending_date
  (our branch, renamed to migration 020_add_subscription_change_pending
   with down_revision updated to chain after 019_add_is_complimentary)

migrations/versions/020_add_subscription_change_pending.py

@@ -0,0 +1,33 @@
+"""Add pending subscription-change columns to user_profiles
+
+Revision ID: 020_add_subscription_change_pending
+Revises: 019_add_is_complimentary
+Create Date: 2026-03-07
+"""
+
+from typing import Union
+
+import sqlalchemy as sa
+from alembic import op
+
+revision: str = "020_add_subscription_change_pending"
+down_revision: Union[str, None] = "019_add_is_complimentary"
+depends_on: Union[str, None] = None
+
+
+def upgrade() -> None:
+    """Add subscription_change_pending_tier and subscription_change_pending_date columns."""
+    op.add_column(
+        "user_profiles",
+        sa.Column("subscription_change_pending_tier", sa.String(50), nullable=True),
+    )
+    op.add_column(
+        "user_profiles",
+        sa.Column("subscription_change_pending_date", sa.DateTime(timezone=True), nullable=True),
+    )
+
+
+def downgrade() -> None:
+    """Remove pending subscription-change columns."""
+    op.drop_column("user_profiles", "subscription_change_pending_date")
+    op.drop_column("user_profiles", "subscription_change_pending_tier")