feat(#415): theme fix, AuthDivider, SessionExpiryWarning components

- AUTH-014: Fix theme storage key (jarvis-theme -> mosaic-theme)
- AUTH-016: Create AuthDivider component with customizable text
- AUTH-019: Create SessionExpiryWarning floating banner (PDA-friendly, blue)
- Fix lint errors in LoginForm, OAuthButton from parallel agents
- Sync pnpm-lock.yaml for recharts dependency

Refs #415

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

apps/web/src/providers/ThemeProvider.tsx

@@ -13,7 +13,7 @@ interface ThemeContextValue {
 
 const ThemeContext = createContext<ThemeContextValue | null>(null);
 
-const STORAGE_KEY = "jarvis-theme";
+const STORAGE_KEY = "mosaic-theme";
 
 function getSystemTheme(): "light" | "dark" {
   if (typeof window === "undefined") return "dark";