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/hooks/useTheme.ts

@@ -1,7 +1,7 @@
 import { lightTheme } from 'folds';
 import { createContext, useContext, useEffect, useMemo, useState } from 'react';
 import { onDarkFontWeight, onLightFontWeight } from '../../config.css';
-import { butterTheme, darkTheme, silverTheme } from '../../colors.css';
+import { butterTheme, darkTheme, lotusTerminalTheme, silverTheme } from '../../colors.css';
 import { settingsAtom } from '../state/settings';
 import { useSetting } from '../state/hooks/settings';
 
@@ -37,6 +37,11 @@ export const ButterTheme: Theme = {
   kind: ThemeKind.Dark,
   classNames: ['butter-theme', butterTheme, onDarkFontWeight, 'prism-dark'],
 };
+export const LotusTerminalTheme: Theme = {
+  id: 'lotus-terminal-theme',
+  kind: ThemeKind.Dark,
+  classNames: ['lotus-terminal-theme', lotusTerminalTheme, onDarkFontWeight, 'prism-dark'],
+};
 
 export const useThemes = (): Theme[] => {
   const themes: Theme[] = useMemo(() => [LightTheme, SilverTheme, DarkTheme, ButterTheme], []);