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/ui/Disclosure.tsx

@@ -0,0 +1,19 @@
+import type { ReactNode } from 'react';
+
+interface DisclosureProps {
+  summary: string;
+  children: ReactNode;
+}
+
+/** Collapsible help/explainer block — keeps secondary content out of the way. */
+export function Disclosure({ summary, children }: DisclosureProps) {
+  return (
+    <details className="glass-sm group">
+      <summary className="flex cursor-pointer select-none items-center gap-2 px-4 py-2.5 text-xs font-medium text-gray-400 transition-colors hover:text-gray-200 [&::-webkit-details-marker]:hidden">
+        <span className="inline-block transition-transform duration-200 group-open:rotate-90">▸</span>
+        {summary}
+      </summary>
+      <div className="px-4 pb-4 pt-1 text-sm text-gray-300">{children}</div>
+    </details>
+  );
+}