style: modern dark UI refresh

- design-token palette (:root vars): deeper #0e0f13 base, indigo #7c8cff accent,
  layered surfaces, softer borders, shadow + radius scale
- tabs as floating rounded chips (active = elevated surface); refined dots
- key bar as rounded chips with gaps; Esc gets the accent tint
- toolbar icon buttons with rounded hover
- overlays (history/dashboard/qr/search/settings) get backdrop-blur + card +
  shadow; indigo primary buttons; consistent inputs with accent focus ring
- chrome uses a system UI font (terminal stays monospace)
- xterm dark theme + meta theme-color + manifest + app icon synced to the
  palette (indigo-gradient icon, accent cursor)
216 tests green; tsc + build clean.

public/settings.ts

@@ -13,14 +13,19 @@ export interface Settings {
 }
 
 export const THEMES: Record<string, ITheme> = {
-  dark: { background: '#1a1a1a', foreground: '#e8e8e8', cursor: '#e8e8e8' },
-  light: {
-    background: '#f5f5f5',
-    foreground: '#1a1a1a',
-    cursor: '#1a1a1a',
-    selectionBackground: '#bcd3f5',
+  dark: {
+    background: '#0e0f13',
+    foreground: '#e7e8ec',
+    cursor: '#7c8cff',
+    selectionBackground: 'rgba(124,140,255,0.28)',
   },
-  solarized: { background: '#002b36', foreground: '#93a1a1', cursor: '#93a1a1' },
+  light: {
+    background: '#f6f7f9',
+    foreground: '#1a1d24',
+    cursor: '#5b6cff',
+    selectionBackground: '#cdd6ff',
+  },
+  solarized: { background: '#002b36', foreground: '#93a1a1', cursor: '#268bd2' },
 }
 
 const KEY = 'web-terminal:settings'