perf(gui): optimize GUI add_dirs allocations and cloning (#191)

* ⚡ Optimize `add_dirs` method by removing redundant allocations

Replaced the `iter().unique().cloned().collect()` pipeline with a simple
contains check before pushing to `app_state.dirs`. This prevents entire
vector allocations and item clones per user folder pick. Furthermore,
saving the configuration and cloning `dirs` is now only performed if the
app state actually changed (e.g. if the user picked a new folder).

Cleaned up the unused `itertools::Itertools` import.

Co-authored-by: arabianq <55220741+arabianq@users.noreply.github.com>

* ⚡ Optimize GUI `add_dirs` allocations and cloning

Replaced the `iter().unique().cloned().collect()` pipeline with a simple
contains check before pushing to `app_state.dirs`. This prevents entire
vector allocations and item clones per user folder pick. Furthermore,
saving the configuration and cloning `dirs` is now only performed if the
app state actually changed (e.g. if the user picked a new folder).

Cleaned up the unused `itertools::Itertools` import. Cargo.lock was
not touched.

Co-authored-by: arabianq <55220741+arabianq@users.noreply.github.com>

---------

Co-authored-by: google-labs-jules[bot] <161369871+google-labs-jules[bot]@users.noreply.github.com>

pwsp-gui/src/gui/mod.rs

@@ -5,7 +5,6 @@ mod views;
 use anyhow::{Result, anyhow};
 use eframe::{NativeOptions, icon_data::from_png_bytes, run_native};
 use egui::{Context, FontData, FontDefinitions, FontFamily, FontTweak, Vec2, ViewportBuilder};
-use itertools::Itertools;
 use pwsp_lib::{
     types::{
         audio_player::PlayerState,
@@ -110,14 +109,19 @@ impl SoundpadGui {
     pub fn add_dirs(&mut self) {
         let file_dialog = FileDialog::new();
         if let Some(paths) = file_dialog.pick_folders() {
+            let mut changed = false;
             for path in paths {
+                if !self.app_state.dirs.contains(&path) {
                     self.app_state.dirs.push(path);
+                    changed = true;
                 }
-            self.app_state.dirs = self.app_state.dirs.iter().unique().cloned().collect();
+            }
+            if changed {
                 self.config.dirs = self.app_state.dirs.clone();
                 self.config.save_to_file().ok();
             }
         }
+    }
 
     pub fn open_dir(&mut self, path: &PathBuf, ctx: Option<Context>, force_rescan: bool) {
         self.app_state.current_dir = Some(path.clone());