feat: Refactor rides app with unique constraints, mixins, and enhanced documentation

- Added migration to convert unique_together constraints to UniqueConstraint for RideModel.
- Introduced RideFormMixin for handling entity suggestions in ride forms.
- Created comprehensive code standards documentation outlining formatting, docstring requirements, complexity guidelines, and testing requirements.
- Established error handling guidelines with a structured exception hierarchy and best practices for API and view error handling.
- Documented view pattern guidelines, emphasizing the use of CBVs, FBVs, and ViewSets with examples.
- Implemented a benchmarking script for query performance analysis and optimization.
- Developed security documentation detailing measures, configurations, and a security checklist.
- Compiled a database optimization guide covering indexing strategies, query optimization patterns, and computed fields.

backend/apps/moderation/selectors.py

@@ -4,7 +4,8 @@ Following Django styleguide pattern for separating data access from business log
 """
 
 from typing import Optional, Dict, Any
-from django.db.models import QuerySet, Count
+from django.db.models import QuerySet, Count, F, ExpressionWrapper, FloatField
+from django.db.models.functions import Extract
 from django.utils import timezone
 from datetime import timedelta
 from django.contrib.auth.models import User
@@ -185,12 +186,14 @@ def moderation_statistics_summary(
     rejected_submissions = handled_queryset.filter(status="REJECTED").count()
 
     # Response time analysis (only for handled submissions)
+    # Security: Using Django ORM instead of raw SQL .extra() to prevent SQL injection
     handled_with_times = (
         handled_queryset.exclude(handled_at__isnull=True)
-        .extra(
-            select={
-                "response_hours": "EXTRACT(EPOCH FROM (handled_at - created_at)) / 3600"
-            }
+        .annotate(
+            response_hours=ExpressionWrapper(
+                Extract(F('handled_at') - F('created_at'), 'epoch') / 3600.0,
+                output_field=FloatField()
+            )
         )
         .values_list("response_hours", flat=True)
     )