fix: add migration for FeedPost.IsHidden and shift management tables

IsHidden was added to FeedPost entity without a corresponding migration,
causing ALL feed_posts queries to fail with PostgresException
("column is_hidden does not exist") in production.

Also captures shift management tables (RecurringShiftPatterns,
ShiftSwapRequests, ShiftWaitlistEntries, ShiftGroupReservations)
that were added to DbContext without a migration.

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

Author: jasperfordesq-ai