Concurrent Libation instances against one LibationFiles folder raced on the
SQLite database, Lucene search index, and log file, and the startup routine
unconditionally deleted LibationContext.db-wal/-shm - discarding committed
transactions when a prior run died abruptly (issue #1931).
- Add SingleInstance (named mutex keyed on the LibationFiles folder). Wire it
into the Avalonia and WinForms startup so a second launch shows a message and
exits before any database access, and holds the lock for the process lifetime.
- DeleteOpenSqliteFiles now skips cleanup when the DB is held by another process
and preserves a non-empty (unrecovered) WAL so SQLite can recover it on open.
Also compare AccountId case-insensitively in AccountsSettings.GetAccount so a
capitalization difference no longer causes spurious 'No account found' errors.
Co-authored-by: rmcrackan <rmcrackan@gmail.com>
