refine: Update network button labels and tooltips with honest security messaging

- Change button labels: 'Extra secure' / 'Normal' (better reflects defense-in-depth)
- Update tooltips to acknowledge CSP already blocks connections:
  - 'Extra secure: Added manual blocking layer (CSP already blocks connections)'
  - 'Normal: Relying on CSP to block connections'
- Update comment: Clarify button adds extra manual layer, not primary control
- More transparent about how security actually works (CSP does the real work)

src/components/Header.tsx

@@ -93,7 +93,7 @@ const Header: React.FC<HeaderProps> = ({
 
           {/* Right: Action Buttons */}
           <div className="flex items-center gap-2">
-            {/* Network availability toggle - Click to disable/enable internet access for maximum security */}
+            {/* Defense-in-depth toggle: Add extra manual blocking layer on top of CSP */}
             <button
               onClick={onToggleNetwork}
               className={`flex items-center gap-1 px-2.5 py-1.5 text-xs rounded-lg font-medium transition-all whitespace-nowrap ${isNetworkBlocked
@@ -101,12 +101,12 @@ const Header: React.FC<HeaderProps> = ({
                 : 'bg-[#16213e] border border-[#39ff14] text-[#39ff14] hover:bg-[#39ff1420]'
                 }`}
               title={isNetworkBlocked
-                ? 'Internet disabled - Maximum security (no data can leave your device)' 
+                ? 'Extra secure: Added manual blocking layer (CSP already blocks connections)'
-                : 'Internet enabled - Normal operation (browser CSP blocks most connections)'}
+                : 'Normal: Relying on CSP to block connections'}
             >
               <span className="text-sm">{isNetworkBlocked ? '🚫' : '🌐'}</span>
               <span className="hidden sm:inline text-[10px]">
-                {isNetworkBlocked ? 'Internet OFF' : 'Internet ON'}
+                {isNetworkBlocked ? 'Extra secure' : 'Normal'}
               </span>
             </button>
           </div>