Add user notification preferences and related API endpoints

- Introduced a new model `UserNotificationPreferences` to store user-specific notification dismissal settings.
- Added context processor to include notification preferences in templates.
- Implemented API endpoints to dismiss backup and AI scanner notifications permanently.
- Updated front-end logic to handle notification dismissal via server-side checks and API calls.
- Enhanced documentation to include a new Custom CSS Guide for theme customization.

baseTemplate/migrations/0002_usernotificationpreferences.py

@@ -0,0 +1,32 @@
+# -*- coding: utf-8 -*-
+# Generated by Django 1.11.29 on 2024-01-01 00:00
+
+from django.conf import settings
+from django.db import migrations, models
+import django.db.models.deletion
+
+
+class Migration(migrations.Migration):
+
+    dependencies = [
+        migrations.swappable_dependency(settings.AUTH_USER_MODEL),
+        ('baseTemplate', '0001_initial'),
+    ]
+
+    operations = [
+        migrations.CreateModel(
+            name='UserNotificationPreferences',
+            fields=[
+                ('id', models.AutoField(auto_created=True, primary_key=True, serialize=False, verbose_name='ID')),
+                ('backup_notification_dismissed', models.BooleanField(default=False, help_text='Whether user has dismissed the backup notification')),
+                ('ai_scanner_notification_dismissed', models.BooleanField(default=False, help_text='Whether user has dismissed the AI scanner notification')),
+                ('created_at', models.DateTimeField(auto_now_add=True)),
+                ('updated_at', models.DateTimeField(auto_now=True)),
+                ('user', models.OneToOneField(on_delete=django.db.models.deletion.CASCADE, related_name='notification_preferences', to=settings.AUTH_USER_MODEL)),
+            ],
+            options={
+                'verbose_name': 'User Notification Preferences',
+                'verbose_name_plural': 'User Notification Preferences',
+            },
+        ),
+    ]