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/styles/globals.css

@@ -54,48 +54,26 @@
     box-shadow: 0 8px 32px rgba(0, 0, 0, 0.2);
   }
 
-  /* Gradient text */
+  /* Gradient text — reserved for the brand wordmark only */
   .text-gradient {
-    background: linear-gradient(135deg, #38bdf8, #818cf8, #a78bfa);
+    background: linear-gradient(135deg, #38bdf8, #60a5fa);
     -webkit-background-clip: text;
     -webkit-text-fill-color: transparent;
     background-clip: text;
   }
 
-  /* Gradient buttons */
-  .btn-gradient {
-    background: linear-gradient(135deg, #3b82f6, #8b5cf6);
+  /* Primary button — single blue accent */
+  .btn-primary {
+    background: rgba(59, 130, 246, 0.85);
     color: white;
-    border: none;
+    border: 1px solid rgba(96, 165, 250, 0.35);
     border-radius: 0.5rem;
     font-weight: 500;
     transition: all 0.2s ease;
-    position: relative;
-    overflow: hidden;
   }
-  .btn-gradient::before {
-    content: '';
-    position: absolute;
-    inset: 0;
-    background: linear-gradient(135deg, #60a5fa, #a78bfa);
-    opacity: 0;
-    transition: opacity 0.2s ease;
-  }
-  .btn-gradient:hover::before {
-    opacity: 1;
-  }
-  .btn-gradient > * {
-    position: relative;
-    z-index: 1;
-  }
-
-  /* Glow accent for active states */
-  .glow-blue {
-    box-shadow: 0 0 20px rgba(59, 130, 246, 0.3), 0 0 60px rgba(59, 130, 246, 0.1);
-  }
-
-  .glow-green {
-    box-shadow: 0 0 20px rgba(16, 185, 129, 0.3), 0 0 60px rgba(16, 185, 129, 0.1);
+  .btn-primary:hover:not(:disabled) {
+    background: rgb(59, 130, 246);
+    box-shadow: 0 0 16px rgba(59, 130, 246, 0.25);
   }
 
   /* Glass input */