Add vacuum method to Indexer for database maintenance

- Added a `vacuum` method in `database.rs` to optimize database file size and performance.
- Integrated `vacuum` calls into `scan.rs` and `index.rs` to ensure regular maintenance during operations.

src/database.rs

@@ -211,10 +211,15 @@ pub mod index {
         VACUUM;
         "#,
       )?;
-      
+
       self.c().execute_batch(SCHEMA)?;
       Ok(())
     }
+    
+    pub fn vacuum(&self) -> rusqlite::Result<()> {
+      self.c().execute("VACUUM;", [])?;
+      Ok(())
+    }
 
     fn digest_file(path: &Path) -> Result<Vec<u8>, Box<dyn std::error::Error>> {
       let mut hasher = blake3::Hasher::new();