feat: add user preferences management and settings UI

[rchandu]

• Implemented user preferences structure and loading/saving functionality in TimerManager.
• Added settings modal for adjusting timer durations and auto-start options.
• Integrated settings button in the main app interface to open the settings modal.
• Updated styles for the settings modal and buttons for better user experience.
• Enhanced timer functionality to reflect user preferences for work and break durations.
• Added reset to defaults functionality in settings.

[Copilot]

Pull Request Overview

This PR adds persistent user preferences management in the backend and a new Settings modal in the UI so users can customize and save timer durations and auto-start options.

• Introduces UserPreferences storage/load/save in TimerManager (Rust).
• Adds a Settings component with a modal UI for editing preferences.
• Integrates a settings button in App.tsx and updates timer buttons to reflect user-configured durations.

Reviewed Changes

Copilot reviewed 10 out of 10 changed files in this pull request and generated 3 comments.

Show a summary per file

File	Description
src/Settings.tsx	New Settings React component; load, update, reset, save
src/Settings.css	Styles for the Settings modal and its controls
src/App.tsx	Added preferences state, settings button, and modal hook
src/App.css	Header and settings button styling
src-tauri/src/lib.rs	TimerManager extended with preferences load/save API
src-tauri/Cargo.toml	Added dirs crate for config directory resolution
eslint.config.js	Added globals configuration for ESLint
package.json	Added globals dependency

Comments suppressed due to low confidence (1)

src-tauri/src/lib.rs:112

• [nitpick] There are no unit tests covering get_preferences and update_preferences. Consider adding tests for loading, updating, and persisting UserPreferences to prevent regressions.

    pub fn update_preferences(&self, new_preferences: UserPreferences) -> Result<(), String> {

[Copilot]

Using onMount twice with a separate handleModalOpen won’t reload preferences each time the modal opens. Replace both onMount blocks with a createEffect that watches props.isOpen to call loadPreferences whenever the modal opens.

Suggested change

	onMount(() => {
	if (props.isOpen) {
	loadPreferences();
	}
	});
	// Load preferences when modal opens
	const handleModalOpen = () => {
	if (props.isOpen) {
	loadPreferences();
	}
	};
	// Watch for isOpen changes
	onMount(() => {
	handleModalOpen();
	});
	// Watch for isOpen changes and load preferences when modal opens
	createEffect(() => {
	if (props.isOpen) {
	loadPreferences();
	}
	});

[Copilot]

Using ok_or("…")? with an &str won’t compile because &str doesn’t implement std::error::Error. Consider returning a concrete error (e.g., io::Error) or converting to a boxed error type.

Suggested change

	.ok_or("Could not get config directory")?;
	.ok_or_else(|| "Could not get config directory".into())?;