Two issues caused the backend to drop and reimport school data on restart:
1. schema_version table was in the drop list inside run_full_migration(),
so after any migration the breadcrumb was destroyed and the next
restart would see no version → re-trigger migration
2. Schema version was set after migration, so a crash mid-migration
left no version → infinite re-migration loop
Fix: remove schema_version from the drop list, and set the version
before running migration so crashes don't cause loops.
Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>
On startup, the app now checks if the database schema version matches
the code. If there's a mismatch or no version exists, it automatically
runs a full data migration before starting.
- Add backend/version.py with SCHEMA_VERSION constant
- Add backend/migration.py with extracted migration logic
- Add SchemaVersion model to track DB version
- Add version check functions to database.py
- Update app.py lifespan to use check_and_migrate_if_needed()
- Simplify migrate_csv_to_db.py to use shared logic
Co-Authored-By: Claude Opus 4.5 <noreply@anthropic.com>
