Scope sign-in routes to Organization

Summary

Implement organization-specific sign-in routes that enforce user authentication scoping based on the organization context. This will ensure users can only authenticate through the appropriate sign-in page for their organization.

Requirements

New Routes

• Create new routes for /o/<organization>/users/sign_in that mirror the existing global sign-in functionality
• Ensure routes handle all necessary authentication actions (GET for form display, POST for authentication, etc.)

Controller Changes

• Update authentication controllers to use the current organization context when looking up users