Fix admin template URL endpoints and registration toggle parameter mismatch

PROBLEMS RESOLVED:

1. Admin Settings Template URL Error:
   - Fixed breadcrumb navigation in admin_settings.html line 14
   - Changed from: url_for('main.admin')
   - Changed to: url_for('main.admin_panel')
   - Matches actual route function name in routes.py

2. Registration Toggle Parameter Mismatch:
   - Fixed admin_users.html registration toggle JavaScript (lines 483-527)
   - Changed from using 'registration_disabled' parameter
   - Changed to using 'registration_enabled' parameter
   - Now matches the admin_registration_settings API endpoint format

3. Registration Toggle Logic Fix:
   - Updated toggle.checked logic to use registration_enabled directly
   - Fixed status text display to show correct enabled/disabled state
   - Corrected AJAX request payload to send registration_enabled boolean

TECHNICAL DETAILS:
- Both templates now use consistent parameter naming with the backend API
- Registration toggle in /admin/users now works correctly with database persistence
- Admin settings breadcrumb navigation no longer throws BuildError
- All admin interfaces now properly integrate with SystemSettings model

This resolves both reported issues:
- '/admin/settings give error' - Fixed URL endpoint mismatch
- 'registration settings in /admin/users keep to show as enabled' - Fixed parameter format

app/templates/main/admin_settings.html

@@ -11,7 +11,7 @@
                 <nav aria-label="breadcrumb">
                     <ol class="breadcrumb">
                         <li class="breadcrumb-item"><a href="{{ url_for('main.dashboard') }}">Dashboard</a></li>
-                        <li class="breadcrumb-item"><a href="{{ url_for('main.admin') }}">Admin</a></li>
+                        <li class="breadcrumb-item"><a href="{{ url_for('main.admin_panel') }}">Admin</a></li>
                         <li class="breadcrumb-item active">System Settings</li>
                     </ol>
                 </nav>
@@ -234,7 +234,7 @@ function toggleRegistration(enabled) {
             'Content-Type': 'application/json',
         },
         body: JSON.stringify({
-            enabled: enabled
+            registration_enabled: enabled
         })
     })
     .then(response => response.json())

app/templates/main/admin_users.html

@@ -487,8 +487,8 @@
                     const toggle = document.getElementById('registrationToggle');
                     const status = document.getElementById('registrationStatus');
                     
-                    toggle.checked = !data.registration_disabled;
-                    status.textContent = data.registration_disabled ? 'Registration Disabled' : 'Registration Enabled';
+                    toggle.checked = data.registration_enabled;
+                    status.textContent = data.registration_enabled ? 'Registration Enabled' : 'Registration Disabled';
                     
                     toggle.addEventListener('change', function() {
                         toggleRegistration(this.checked);
@@ -501,7 +501,7 @@
         }
 
         function toggleRegistration(enabled) {
-            const data = { registration_disabled: !enabled };
+            const data = { registration_enabled: enabled };
             
             fetch('/admin/settings/registration', {
                 method: 'POST',
@@ -516,7 +516,7 @@
                     showAlert(data.error, 'error');
                 } else {
                     const status = document.getElementById('registrationStatus');
-                    status.textContent = data.registration_disabled ? 'Registration Disabled' : 'Registration Enabled';
+                    status.textContent = data.registration_enabled ? 'Registration Enabled' : 'Registration Disabled';
                     showAlert(data.message, 'success');
                 }
             })