Feat: Implement dynamic internal column protection and Fullscreen mode.

- Internal control columns (Type, Checking, etc.) now persist across Excel shifts.
- Master data columns now prioritize Dropbox source of truth.
- Added Fullscreen mode to all main tabs (Pricing, Descriptions, Matrix).
- Improved Supabase data loading with pagination.

src/components/PricingView.tsx

@@ -656,12 +656,11 @@ export function PricingView({ data, headers, onSaveRow, onCaptureState, onEdit,
   ];
 
   return (
-    <div className={isFullscreen ? "fixed inset-0 z-40 bg-[#041021] p-4 overflow-auto" : "space-y-6"}>
+    <div className={isFullscreen ? "fixed inset-0 z-[100] bg-[#041021] p-6 overflow-auto" : "space-y-6"}>
       {isFullscreen && (
         <button
           onClick={() => setIsFullscreen(false)}
-          className="fixed top-4 right-4 z-50 w-10 h-10 flex items-center justify-center bg-slate-800/90 backdrop-blur border border-slate-600 text-white rounded hover:bg-slate-700 hover:scale-105 transition-all"
-          title="Exit fullscreen"
+          className="fixed top-4 right-4 z-[110] p-2 bg-slate-800 hover:bg-slate-700 text-slate-200 rounded-md transition-colors border border-slate-700"
         >
           <X className="w-5 h-5" />
         </button>