fix(alembic): renumber benchmark migration 011 -> 012

011 collided with the existing 011_add_regime_snapshots (duplicate revision id
and a second head branching off 010), which broke `alembic upgrade head`. Chain
the benchmark_prices migration after regime_snapshots so the history is linear
again (010 -> 011 regime_snapshots -> 012 benchmark_prices, single head).

Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>

alembic/versions/012_add_benchmark_prices.py

@@ -5,8 +5,8 @@ return minus the benchmark's return over the same holding period — can be
 computed. Kept separate from the tradeable universe: the benchmark is not a
 Ticker, so it never enters the scanner, momentum ranking, or rankings.
 
-Revision ID: 011
-Revises: 010
+Revision ID: 012
+Revises: 011
 Create Date: 2026-06-28 00:00:00.000000
 
 """
@@ -17,8 +17,8 @@ import sqlalchemy as sa
 
 
 # revision identifiers, used by Alembic.
-revision: str = "011"
-down_revision: Union[str, None] = "010"
+revision: str = "012"
+down_revision: Union[str, None] = "011"
 branch_labels: Union[str, Sequence[str], None] = None
 depends_on: Union[str, Sequence[str], None] = None