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/auth/AuthLayout.tsx

@@ -135,7 +135,7 @@ export function AuthLayout() {
           <Header className={css.AuthHeader} size="600" variant="Surface">
             <Box grow="Yes" direction="Row" gap="300" alignItems="Center">
               <img className={css.AuthLogo} src={LotusLogo} alt="Lotus Chat Logo" />
-              <Text size="H3">Cinny</Text>
+              <Text size="H3">Lotus Chat</Text>
             </Box>
           </Header>
           <Box className={css.AuthCardContent} direction="Column">