The v15 test pattern (delete migration records >= 15, drop schema, reopen to replay)
was failing because outreach_shared_number_overrides table from v19 migration was not
dropped before replaying. Add DROP TABLE IF EXISTS to the schema cleanup block to
match the same fix applied to v17 test.
This resolves the 'table already exists' error during v19 migration replay.
Co-Authored-By: Claude Sonnet 5 <noreply@anthropic.com>