Add Lotus Terminal Mode + fix all remaining Cinny branding

- New: Lotus Terminal Mode toggle in Appearance settings
  - Red phosphor color scheme (bg #0a0000, primary #ff3300, accent #00dd66)
  - Monospace font override (JetBrains Mono / Fira Code / Cascadia Code)
  - Retro CRT scanline overlay via CSS pseudo-element
  - Wired into ThemeManager with dedicated lotusTerminalBodyClass
- Branding: replace all user-visible Cinny references with Lotus Chat
  - WelcomePage, AuthLayout, SplashScreen, index.html meta tags
  - Device display names in login/register/token flows
  - System notification brand field
  - (Preserved internal Matrix protocol CinnySpaces event type)

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

src/app/state/settings.ts

@@ -42,6 +42,7 @@ export interface Settings {
   dateFormatString: string;
 
   developerTools: boolean;
+  lotusTerminal: boolean;
 
   chatBackground: ChatBackground;
   perMessageProfiles: boolean;
@@ -79,6 +80,7 @@ const defaultSettings: Settings = {
   dateFormatString: 'D MMM YYYY',
 
   developerTools: false,
+  lotusTerminal: false,
 
   chatBackground: 'none',
   perMessageProfiles: false,