Apply the theme from PageSettings in JS, before the first paint

wwwroot/js/theme.js now picks the theme. It sets data-theme (neo-light or
neo-dark, or none when the OS decides) and the hue and chroma variables on
<html>, using the same flag precedence as the old CascadingState branches. It
also keeps <meta name="theme-color"> in sync. Because it runs in <head> from the
settings saved in localStorage, a reload no longer flashes the default palette
before Blazor boots. With system theming it also follows the OS when the colour
scheme changes.

CascadingState loses its ~200 lines of generated <style> and <Meta> tags. It now
calls AppStatusService.ApplyTheme on load and whenever the settings change. The
--fa-* icon colour variables are gone; nothing read them.

Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_01LsXgEaXee4GCU1hwYgPJXw

wwwroot/index.html

@@ -8,6 +8,8 @@
 	<base href="/" />
 	<link href="vendor/ionicons.min.css" rel="stylesheet" />
 	<link href="css/app.css" rel="stylesheet" />
+	<meta name="theme-color" content="hsl(0 0% 88%)" />
+	<script src="js/theme.js"></script>
 	<link href="manifest.json" rel="manifest" />
 	<link rel="apple-touch-icon" sizes="512x512" href="imgs/icon-512.png" />
 	<link rel="apple-touch-icon" sizes="192x192" href="imgs/icon-192.png" />