feat: add theme provider and control components for light/dark mode

- Implemented ThemeProvider to manage theme state and preferences.
- Added ThemeControl component for users to switch between system, light, and dark themes.
- Integrated localStorage for theme preference persistence.
- Updated document styles based on theme changes.

test: add tests for permanent deletion of habits and related records

- Created tests to ensure permanent deletion of habits removes all dependent records.
- Verified that deletion requires ownership, authentication, and checks for archived habits.
- Added tests to confirm rollback behavior on deletion failures.

test: add tests for habit palette and progress card functionality

- Implemented tests for habit color progression and theme-based color shading.
- Added tests for progress card calculations and calendar display logic.

feat: define theme types and preferences

- Introduced Theme and ThemePreference types for better type safety.
- Created utility functions for resolving theme based on user preference and system settings.
- Defined theme palettes for light and dark modes to ensure adequate contrast.

src/components/design-system/Modal.tsx

@@ -53,7 +53,7 @@ export function Modal({ id, eyebrow, title, description, children, onClose, clos
     onKeyDown={event => {
       if (event.key !== "Tab") return;
       event.stopPropagation();
-      const controls = [...event.currentTarget.querySelectorAll<HTMLElement>('button, a[href], input, select, textarea, [tabindex]')]
+      const controls = [...event.currentTarget.querySelectorAll<HTMLElement>('button, a[href], input, select, textarea, summary, [tabindex]')]
         .filter(element => element.tabIndex >= 0 && !element.matches(':disabled') && element.getClientRects().length > 0);
       const first = controls[0];
       const last = controls.at(-1);