don't use strings for paths

src/options.rs

@@ -1,3 +1,5 @@
+use std::path::PathBuf;
+
 #[derive(Debug, Clone, PartialEq, Eq)]
 pub enum BackendType {
     Redb,
@@ -7,7 +9,7 @@ pub enum BackendType {
 
 #[derive(Debug, Clone)]
 pub struct DBOption {
-    pub dir: String,
+    pub dir: PathBuf,
     pub port: u16,
     pub debug: bool,
     // Deprecated for data DBs; retained for backward-compat on CLI parsing