Added foundational modules for core functionalities:

- Introduced `walk.rs` as a parallel directory walker for search operations.
- Implemented basic index handling in `commands/index.rs`.
- Created `utils/config.rs` for configuration management with placeholders for future enhancements.

src/commands/mod.rs

@@ -0,0 +1,29 @@
+pub mod scan;
+pub mod index;
+pub mod list;
+pub mod clean;
+
+use crate::cli::Commands;
+use std::path::Path;
+use crate::utils::config::Config;
+
+pub fn handle_command(
+    command: Commands,
+    database_dir: &Path,
+    config: &Config
+) -> Result<(), Box<dyn std::error::Error>> {
+    match command {
+        Commands::Scan { path, no_index, rebuild_index, format, high_only } => {
+            scan::handle(&path, no_index, rebuild_index, format, high_only, database_dir, config)
+        }
+        Commands::Index { action } => {
+            index::handle(action, database_dir)
+        }
+        Commands::List { verbose } => {
+            list::handle(verbose, database_dir)
+        }
+        Commands::Clean { project, all } => {
+            clean::handle(project, all, database_dir)
+        }
+    }
+}