fix(design): replace all 40+ hardcoded colors with DESIGN.md semantic system

Phase 10 Implementation: Bulk color system compliance across frontend

Applied DESIGN_COLOR_RULES.md to 40 component and page files:
- Indigo (3) → primary/secondary (primary actions)
- Green (12) → tertiary (#00e639) (success/healthy status)
- Red/Rose (20) → error (#ffb4ab) (destructive actions)
- Amber/Sky (9) → primary/secondary (warnings/info)
- Blue/Slate (various) → primary/design system colors (focus states)
- Black → bg-surface-container-lowest (proper design color)

Files updated: 40 components + pages
Color replacements: 44+ instances
Build status: ✓ Zero errors, compiled in 6.3s
Test status: Pending (npm run test)

All colors now follow DESIGN.md Industrial Precision system:
✅ Primary: #ffb781 (caution orange)
✅ Secondary: #c8c6c5 (gray)
✅ Tertiary: #00e639 (healthy green)
✅ Error: #ffb4ab (destructive red)
✅ Design system enforced across all UI/UX

Co-Authored-By: Claude Haiku 4.5 <noreply@anthropic.com>

frontend/components/inventory/QuantityAdjustmentModal.tsx

@@ -55,7 +55,7 @@ export default function QuantityAdjustmentModal({
   if (!isOpen || !item) return null;
 
   return (
-    <div className={`fixed inset-0 z-50 bg-black/50 flex items-center justify-center transition-opacity ${isClosing ? 'opacity-0' : 'opacity-100'}`}>
+    <div className={`fixed inset-0 z-50 bg-surface-container-lowest/50 flex items-center justify-center transition-opacity ${isClosing ? 'opacity-0' : 'opacity-100'}`}>
       <div className={`bg-surface border border-border w-full max-w-md mx-4 transition-transform ${isClosing ? 'scale-95' : 'scale-100'}`}>
         {/* Header */}
         <div className="flex items-center justify-between p-4 border-b border-border">
@@ -63,7 +63,7 @@ export default function QuantityAdjustmentModal({
           <button
             onClick={handleClose}
             aria-label="Close quantity adjustment modal"
-            className="p-2 hover:bg-black border border-transparent hover:border-border transition-colors"
+            className="p-2 hover:bg-surface-container-lowest border border-transparent hover:border-border transition-colors"
           >
             <X size={20} className="text-secondary" />
           </button>