Add dynamic Terms of Service URL configuration

[heysamtexas]

Description

Allow admins to configure Terms of Service URL dynamically through Django admin instead of hardcoding links.

Current State

ToS links are likely hardcoded or missing from the application.

Proposed Implementation

Add field to SiteConfiguration model:

• terms_of_service_url - URLField for ToS link
• terms_required - BooleanField to require acceptance

Benefits

• Easy updates to legal documents
• Compliance with changing regulations
• No code deployments for legal updates

Acceptance Criteria

• Add ToS URL field to SiteConfiguration
• Display ToS link in footer and registration
• Optional: Add ToS acceptance checkbox to signup
• Validate URL format
• Test link functionality

Labels: enhancement, ui/ux, legal
Priority: Medium