Add repair_migrations Tauri command that deletes stale migration 1
checksum from _sqlx_migrations before Database.load(). Migration 1
is idempotent (CREATE IF NOT EXISTS) so re-applying is safe.
Fixes "migration 1 was previously applied but has been modified".
Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>
Each profile gets its own SQLite database file for complete data isolation.
Profile selection screen at launch, sidebar switcher for quick switching,
and optional 4-6 digit PIN for privacy. Existing database becomes the
default profile with seamless upgrade.
Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>