docs(a11y): add accessibility testing guide and reduced motion support - Phase 3

Add comprehensive accessibility testing documentation:
- Keyboard navigation testing flows (5 detailed test scenarios)
- Screen reader testing guide (VoiceOver, Narrator)
- Color contrast testing procedures
- Mobile accessibility requirements
- Touch target size validation
- Tool recommendations (Axe, WAVE, Lighthouse)
- Issue reporting template
- WCAG 2.1 Level AA compliance tracking

Accessibility improvements:
- Add prefers-reduced-motion media query to globals.css
- Disable animations/transitions for users with reduced motion preference
- Respect animation timing preferences
- Improve experience for motion-sensitive users

This completes the 3-phase accessibility overhaul and establishes
ongoing testing and compliance procedures.

frontend/app/globals.css

@@ -64,3 +64,28 @@ body {
 .pt-safe {
   padding-top: env(safe-area-inset-top);
 }
+
+/* Accessibility: Respect user's reduced motion preference */
+@media (prefers-reduced-motion: reduce) {
+  *,
+  *::before,
+  *::after {
+    animation-duration: 0.01ms !important;
+    animation-iteration-count: 1 !important;
+    transition-duration: 0.01ms !important;
+  }
+
+  /* Disable keyframe animations */
+  @keyframes scan {
+    0%, 100% { top: 0%; }
+    50% { top: 100%; }
+  }
+
+  .animate-spin-slow {
+    animation: none !important;
+  }
+
+  .animate-pulse {
+    animation: none !important;
+  }
+}