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/parks/models/parks.py

@@ -127,6 +127,8 @@ class Park(StateMachineMixin, TrackedModel):
     # Timezone for park operations
     timezone = models.CharField(
         max_length=50,
+        default='UTC',
+        blank=True,
         help_text="Timezone identifier for park operations (e.g., 'America/New_York')"
     )