Function db_path 

pub fn db_path(override_path: Option<&Path>) -> PathBuf

Resolve the path to the index database.

When override_path is Some, it is used verbatim — this is what the CLI’s --db flag wires into. Otherwise the default ~/.logdive/index.db is returned per the “Default index location” decision in the project doc.

Purely functional: does not touch the filesystem.