fix(manage-api): CORS auth headers case sensitivity and base domain matching

[amikofalvy]

Summary

• Fixes CORS preflight failures for auth routes on deployed instances by including both lowercase and uppercase header variants (content-type, Content-Type, authorization, Authorization) in allowHeaders
• Adds getBaseDomain function to extract base domain from hostnames (e.g., agents-manage-ui.preview.inkeep.com → preview.inkeep.com)
• Updates isOriginAllowed to support same base domain matching for preview deployments, allowing cross-origin requests between agents-manage-ui.preview.inkeep.com and agents-manage-api.preview.inkeep.com

Problem

Access to fetch at 'https://agents-manage-api.preview.inkeep.com/api/auth/sign-in/email' from origin 'https://agents-manage-ui.preview.inkeep.com' has been blocked by CORS policy: Request header field content-type is not allowed by Access-Control-Allow-Headers in preflight response.

Test plan

• [ ] Verify auth sign-in works on preview deployments
• [ ] Verify CORS preflight requests return correct Access-Control-Allow-Headers

[changeset-bot[bot]]

⚠️ No Changeset found

Latest commit: 5185a93e06ef37307e1954da1f7272507a300078

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Project	Deployment	Preview	Comments	Updated (UTC)
agents-manage-api	Ready	Preview	Comment	Dec 2, 2025 6:35pm
agents-manage-ui	Ready	Preview	Comment	Dec 2, 2025 6:35pm
agents-run-api	Ready	Preview	Comment	Dec 2, 2025 6:35pm

1 Skipped Deployment

Project	Deployment	Preview	Comments	Updated (UTC)
agents-docs	Skipped			Dec 2, 2025 6:35pm