refactor: modularize CLI and optimize cache metadata lookups

- Extract error handling, path validation, and handlers into separate modules
- Add CacheCheckResult to pre-fetch metadata and avoid double lookups
- Deprecate legacy cache methods in favor of optimized alternatives
- Enable tokio fs feature for async file operations
- Remove debug profile from release build

src/cli/handlers/undo.rs

@@ -0,0 +1,53 @@
+use crate::cli::Args;
+use crate::cli::path_utils::validate_and_normalize_path;
+use crate::settings::Config;
+use crate::storage::UndoLog;
+use colored::*;
+use std::path::PathBuf;
+
+pub async fn handle_undo(
+    args: Args,
+    download_path: PathBuf,
+) -> Result<(), Box<dyn std::error::Error>> {
+    let undo_log_path = Config::get_undo_log_path()?;
+
+    if !undo_log_path.exists() {
+        println!("{}", "No undo log found. Nothing to undo.".yellow());
+        return Ok(());
+    }
+
+    let mut undo_log = UndoLog::load_or_create(&undo_log_path);
+
+    if !undo_log.has_completed_moves() {
+        println!("{}", "No completed moves to undo.".yellow());
+        return Ok(());
+    }
+
+    // Use custom path if provided, otherwise use the configured download path
+    let target_path = args.path.unwrap_or(download_path);
+
+    // Validate and normalize the target path early
+    let target_path = match validate_and_normalize_path(&target_path).await {
+        Ok(normalized) => normalized,
+        Err(e) => {
+            println!("{}", format!("ERROR: {}", e).red());
+            return Ok(());
+        }
+    };
+
+    crate::files::undo_moves(&target_path, &mut undo_log, args.dry_run)?;
+
+    if let Err(e) = undo_log.save(&undo_log_path) {
+        eprintln!(
+            "{}",
+            format!(
+                "WARNING: Failed to save undo log to '{}': {}. Your undo history may be incomplete.",
+                undo_log_path.display(),
+                e
+            )
+            .yellow()
+        );
+    }
+
+    Ok(())
+}