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/pages/client/WelcomePage.tsx

@@ -15,7 +15,7 @@ export function WelcomePage() {
         <PageHeroSection>
           <PageHero
             icon={<img width="70" height="70" src={CinnySVG} alt="Lotus Chat Logo" />}
-            title="Welcome to Cinny"
+            title="Welcome to Lotus Chat"
             subTitle={
               <span>
                 Yet another matrix client.{' '}