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/inventory/page.tsx

@@ -385,7 +385,7 @@ export default function InventoryPage() {
 
       {/* Stock Adjustment / Edit Item Overlay */}
       {selectedItem && (
-        <div className="fixed inset-0 z-50 flex items-end sm:items-center justify-center p-0 sm:p-4 bg-slate-950/80 backdrop-blur-sm animate-in fade-in duration-200">
+        <div className="fixed inset-0 z-50 flex items-end sm:items-center justify-center p-0 sm:p-4 bg-slate-950/80 animate-in fade-in duration-200">
           <div className="w-full max-w-lg bg-slate-900 border-x border-t sm:border border-slate-800 rounded-t-[2.5rem] sm:rounded-[2.5rem] shadow-2xl p-5 sm:p-8 overflow-hidden animate-in slide-in-from-bottom-10 duration-300">
               <div className="flex justify-between items-center mb-6">
                 <h3 className="text-xl font-black tracking-tight flex items-center gap-2">
@@ -631,7 +631,7 @@ export default function InventoryPage() {
 
       {/* Category Edit Overlay */}
       {editingCategory && (
-        <div className="fixed inset-0 z-50 flex items-center justify-center p-4 bg-slate-950/90 backdrop-blur-xl animate-in fade-in duration-300">
+        <div className="fixed inset-0 z-50 flex items-center justify-center p-4 bg-slate-950/90 animate-in fade-in duration-300">
           <div className="bg-slate-900 border border-slate-800 rounded-3xl p-8 max-w-sm w-full shadow-2xl space-y-6 animate-in zoom-in-95 duration-200">
             <div className="flex justify-between items-center">
                <h2 className="text-xl font-black">Edit Category</h2>
@@ -680,7 +680,7 @@ export default function InventoryPage() {
 
       {/* Box Manager Modal */}
       {showBoxManager && (
-        <div className="fixed inset-0 z-50 flex items-center justify-center p-4 bg-slate-950/90 backdrop-blur-md animate-in fade-in duration-300">
+        <div className="fixed inset-0 z-50 flex items-center justify-center p-4 bg-slate-950/90 animate-in fade-in duration-300">
           <div className="w-full max-w-2xl bg-slate-900 border border-slate-800 rounded-[2.5rem] shadow-2xl overflow-hidden flex flex-col max-h-[90vh]">
             <div className="p-8 pb-4 flex flex-col gap-6 shrink-0 bg-slate-900/50">
                <div className="flex justify-between items-center">