## ADDED Requirements

### Requirement: User can switch between light and dark themes
The system SHALL allow the user to toggle between light and dark themes with a persistent preference.

#### Scenario: User toggles dark mode on
- **WHEN** the user activates the theme toggle while the app is in light mode
- **THEN** the system applies the dark theme and saves the preference for future visits

#### Scenario: User toggles dark mode off
- **WHEN** the user activates the theme toggle while the app is in dark mode
- **THEN** the system applies the light theme and saves the preference for future visits

### Requirement: Theme preference respects system defaults on first visit
The system SHALL use the user's system color scheme preference when no saved preference exists.

#### Scenario: No stored preference uses system theme
- **WHEN** the user opens the app for the first time without a saved theme preference
- **THEN** the system applies dark mode when the operating system prefers dark color schemes and light mode otherwise

### Requirement: Theme selection loads without a flash of the wrong theme
The system SHALL initialize the theme before the first visible paint so the page does not briefly render in the wrong theme.

#### Scenario: Initial paint matches saved theme
- **WHEN** the app loads and a saved theme preference exists
- **THEN** the document theme is applied before the page content is visibly rendered