refactor(frontend): eliminate backdrop-blur throughout codebase

Remove all instances of backdrop-blur effect (14+ occurrences) to simplify visual design
and eliminate signature 2023-2024 AI aesthetic tell. Components now use solid backgrounds
and borders for hierarchy and affordance instead of decorative blur.

Affected:
- BottomNav: solid bg-slate-950, clean border
- AdminOverlay: removed overlay blur
- Admin managers (Identity, Database, AI, Category, LDAP): removed glass-card aesthetic
- Modals (IdentityCheck, Scanner, AIOnboarding): removed decorative blur
- Page layouts (home, inventory, logs): removed modal backdrop blur
- globals.css: removed glass-card utility

Build: passes with zero errors. Bundle sizes unchanged.

Simplification improves: clarity, perceived intentionality, removes AI aesthetic tells.

frontend/app/globals.css

@@ -36,13 +36,9 @@ body {
   background: #334155; /* slate-700 */
 }
 
-/* Modern Utility for Premium Glassmorphism */
+/* Removed: glass-card utility (eliminated glassmorphism aesthetic) */
 @layer utilities {
-  .glass-card {
-    @apply bg-slate-900/40 backdrop-blur-xl border border-slate-800/50 shadow-2xl;
-    background-image: linear-gradient(135deg, rgba(255,255,255,0.02) 0%, rgba(255,255,255,0) 100%);
-  }
-  
+
   .text-fluid-lg {
     font-size: clamp(1.125rem, 3cqi, 1.5rem);
   }