## ADDED Requirements

### Requirement: Theme persistence works across visits with fallback
The site MUST persist the user's theme selection across visits so returning users see the last-selected theme.

The site MUST use client-side persistence and MUST support a fallback mechanism:
- Primary: `localStorage`
- Fallback: a client-side cookie

The effective theme selection order MUST be:
1) Stored theme in `localStorage` (if available)
2) Stored theme in a cookie (if localStorage is unavailable)
3) Default selection using environment signals

#### Scenario: LocalStorage persists across a later visit
- **WHEN** a user selects `light` theme and later returns to the site in the same browser
- **THEN** the site initializes in `light` theme before first paint

#### Scenario: Cookie fallback is used when localStorage is unavailable
- **WHEN** the browser environment blocks `localStorage` access and the user selects `dark` theme
- **THEN** the theme is persisted using a client-side cookie and is restored on the next visit

#### Scenario: No persistence available falls back to defaults
- **WHEN** both `localStorage` and cookie persistence are unavailable
- **THEN** the site falls back to default theme selection using environment signals
