feat: implement api crud for brand and theme color

[ngovinh2k2]

What?

Implement API crud for brand and theme color

Why?

How?

Testing?

• Functional Testing
• Security
• Performance
• Error Handling
• Code Quality
• Documentation
• Database
• Deployment
• Final Review

Anything Else?

[gemini-code-assist]

Code Review

This pull request introduces a new organization_setting application to manage organization-specific settings and themes (light and dark). It includes database models, serializers, views, URLs, a backfill migration, and integrates settings into the bootstrap process and organization API. The review feedback highlights several critical issues: a potential TypeError in the serializer's _get_instance method when no default is provided, a likely IntegrityError during bulk_create due to missing UUID generation, dead lookup code caused by read-only nested id fields, an anti-pattern of importing application services inside a migration, and a lack of validation for the X-Organization header in the settings view.

Important

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