fix: rename branching migration to 067 to avoid duplicate revision ID

030 was already taken by 030_enhance_invite_codes.py.

Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>

backend/alembic/versions/067_add_conversational_branching.py

@@ -1,13 +1,13 @@
 """Add conversational branching tables and columns.
 
-Revision ID: 030
+Revision ID: 067
 """
 from alembic import op
 import sqlalchemy as sa
 from sqlalchemy.dialects.postgresql import UUID, JSONB
 
-revision = "030"
-down_revision = "066"  # from alembic heads
+revision = "067"
+down_revision = "066"
 branch_labels = None
 depends_on = None