feat: Add 10-second timeout for admin re-authentication

Security enhancement:
- Admin must re-enter password if Settings closed >10 seconds
- localStorage stores admin_close_time when closing Settings
- toggleSettings() checks elapsed time since last close
- If elapsed >10s: clear token, show login modal
- If elapsed <=10s: open Settings directly (no password)

Implementation:
- Added localStorage.admin_close_time tracking
- Modified toggleSettings() to check timeout
- Clear close_time when opening Settings
- Clear close_time on new login
- Clear close_time when token removed

User workflow:
1. Login → Settings open
2. Close Settings → record close_time
3. Re-open immediately (<10s) → direct access
4. Re-open after 10s → password required

Files changed: src/page.html (+15 lines in toggleSettings, +1 line in submitAdminLogin)

Security: Prevents unauthorized access if admin leaves Settings open and returns later

src/page.html

@@ -137,8 +137,22 @@ var _sv=false;
 
 function toggleSettings(){
     var token=localStorage.getItem('admin_token');
+    var lastClose=localStorage.getItem('admin_close_time');
     
     if(token){
+        // Check if closed more than 10 seconds ago
+        if(lastClose){
+            var now=Date.now();
+            var elapsed=(now-parseInt(lastClose))/1000;
+            if(elapsed>10){
+                // Token expired (>10s since close), clear and show login
+                localStorage.removeItem('admin_token');
+                localStorage.removeItem('admin_close_time');
+                showAdminLoginModal();
+                return;
+            }
+        }
+        
         // Verify token validity
         fetch('/api/v2/admin/verify',{
             headers:{'Authorization':'Bearer '+token}
@@ -149,15 +163,24 @@ function toggleSettings(){
                 // Token valid, open settings
                 _sv=!_sv;
                 document.getElementById("mb-settings-panel").classList.toggle("active",_sv);
-                if(_sv)loadSettings();
+                if(_sv){
+                    loadSettings();
+                    // Clear close time when opening
+                    localStorage.removeItem('admin_close_time');
+                }else{
+                    // Record close time when closing
+                    localStorage.setItem('admin_close_time',Date.now());
+                }
             }else{
                 // Token invalid, remove and show login
                 localStorage.removeItem('admin_token');
+                localStorage.removeItem('admin_close_time');
                 showAdminLoginModal();
             }
         })
         .catch(function(e){
             localStorage.removeItem('admin_token');
+            localStorage.removeItem('admin_close_time');
             showAdminLoginModal();
         });
     }else{
@@ -203,6 +226,7 @@ function submitAdminLogin(){
     .then(function(d){
         if(d.token){
             localStorage.setItem('admin_token',d.token);
+            localStorage.removeItem('admin_close_time'); // Clear close time on new login
             document.getElementById('mb-admin-modal').classList.remove('active');
             toast('Admin authenticated ✓');
             toggleSettings(); // Re-open settings