UI/UX redesign: unified refined-glass design system

- Add shared UI primitives: Button, Field/Input/Select, PageHeader,
  Section, Callout, Tabs, Disclosure
- Replace gradient buttons with single blue-accent btn-primary
- Reserve gradient text for the brand wordmark only
- Rework Scanner page onto the glass system; collapse explainer and
  glossary into a disclosure, move filters into a glass toolbar
- Restructure Ticker Detail into tabs (Analysis / Indicators / S/R)
  with chart and recommendation always visible
- Align Watchlist, Rankings, Admin, Login/Register to shared primitives
- Unify stray indigo/violet/gray accents into the blue family

Co-Authored-By: Claude Fable 5 <noreply@anthropic.com>

frontend/src/components/admin/RecommendationSettings.tsx

@@ -89,7 +89,7 @@ export function RecommendationSettings() {
       </div>
 
       <div className="flex items-center gap-2">
-        <button className="btn-gradient px-4 py-2 text-sm" onClick={onSave} disabled={update.isPending}>
+        <button className="btn-primary px-4 py-2 text-sm" onClick={onSave} disabled={update.isPending}>
           {update.isPending ? 'Saving…' : 'Save Configuration'}
         </button>
         <button className="px-4 py-2 text-sm rounded border border-white/[0.1] text-gray-300 hover:text-white" onClick={onReset} disabled={update.isPending}>