Implement site settings backend and bulk visibility apply

app/routes/admin.py

@@ -5,6 +5,7 @@ from app import db
 from app.models.user import User
 from app.models.set import Set
 from app.models.instruction import Instruction
+from app.models.site_setting import SiteSetting, VISIBILITIES
 from sqlalchemy import func
 from datetime import datetime, timedelta
 
@@ -218,8 +219,33 @@ def delete_set(set_id):
 def site_settings():
     """Site-wide settings configuration."""
     if request.method == 'POST':
-        # This is a placeholder for future site settings
-        # You could store settings in a database table or config file
+        action = request.form.get('action', 'save')
+
+        if action == 'apply_visibility':
+            # Bulk-apply one visibility to every existing set. Handy right
+            # after an upgrade, when old sets are all still public.
+            target = request.form.get('bulk_visibility', '')
+            if target not in VISIBILITIES:
+                flash('Unknown visibility setting.', 'danger')
+                return redirect(url_for('admin.site_settings'))
+            changed = Set.query.update({Set.visibility: target},
+                                       synchronize_session=False)
+            db.session.commit()
+            flash(f'Set {changed} existing set(s) to {target}.', 'success')
+            return redirect(url_for('admin.site_settings'))
+
+        SiteSetting.set('allow_registration',
+                        request.form.get('allow_registration') == 'on')
+        SiteSetting.set('home_redirect_dashboard',
+                        request.form.get('home_redirect_dashboard') == 'on')
+
+        default_visibility = request.form.get('default_visibility', 'private')
+        if default_visibility not in VISIBILITIES:
+            default_visibility = 'private'
+        SiteSetting.set('default_visibility', default_visibility)
+
+        db.session.commit()
+        SiteSetting.clear_cache()
         flash('Settings updated successfully', 'success')
         return redirect(url_for('admin.site_settings'))
     
@@ -231,7 +257,16 @@ def site_settings():
         'total_storage': db.session.query(func.sum(Instruction.file_size)).scalar() or 0
     }
     
-    return render_template('admin/settings.html', stats=stats)
+    visibility_counts = dict(
+        db.session.query(Set.visibility, func.count(Set.id))
+        .group_by(Set.visibility).all()
+    )
+
+    return render_template('admin/settings.html',
+                           stats=stats,
+                           settings=SiteSetting.all_settings(),
+                           visibilities=VISIBILITIES,
+                           visibility_counts=visibility_counts)
 
 
 @admin_bp.route('/api/stats')
@@ -332,6 +367,7 @@ def bulk_import():
                     year_released=set_data.get('year', datetime.now().year),
                     piece_count=set_data.get('pieces', 0),
                     image_url=set_data.get('image', {}).get('imageURL'),
+                    visibility=SiteSetting.get('default_visibility', 'private'),
                     user_id=user_id,
                     is_moc=False
                 )