N3: LeiosDbConfig configuration entry + thread to consensus
Introduces 'Cardano.Node.Configuration.Leios.LeiosDbConfig' with two
constructors:
- LeiosDbInMemory (matches 'LeiosDbConnection's in-memory backend)
- LeiosDbSQLite !FilePath (SQLite backend, file relative to node CWD)
Wired through 'PartialNodeConfiguration' / 'NodeConfiguration' as
'ncLeiosDbConfig' with JSON parsing ('"LeiosDbConfig":{"Backend":...,
"Filepath":...}') and a default of 'LeiosDbSQLite "leios.db"'.
At node startup ('Cardano.Node.Run.handleSimpleNode'), the configured
backend is materialised into a 'LeiosDbHandle' (via 'newLeiosDBInMemory'
/ 'newLeiosDBSQLite') and passed into 'RunNodeArgs' through a new
'rnLeiosDb :: Maybe (LeiosDbHandle m)' field, which consensus's
'runWith' threads into the Leios kernel's shared connection.
'Nothing' falls back to the in-memory default.
Co-Authored-By: Claude Opus 4.7 <[email protected]>