feat: add API to create anonymous projects with 3-project limit

[iamanishsrivastava]

Add API to create anonymous projects with 3-project limit

🚀 Feature Request

Allow anonymous users to create projects using a persistent client ID and enforce a maximum project limit of 3.

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🎯 Motivation

Letting users try the product without signing up improves onboarding. Limiting the number prevents abuse.

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🧩 Solution or Approach

• Store anonymous ID in frontend
• On project creation, backend looks up/creates AnonymousUser
• Check project count < 3
• If valid, create project linked to anonymousUserId

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✅ Acceptance Criteria

• Accept anonymous user ID in POST body/header
• Return error if project count ≥ 3
• Save new project to DB if allowed

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📎 Additional Context

Requires schema setup (#1).

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🔀 Related Branch

feat/anonymous-project-create

[github-actions]

This GitHub issue proposes adding a new API endpoint under the feat/anonymous-project-create branch to enable the creation of anonymous projects. The feature will include logic to enforce a limit of three projects per anonymous user. Additionally, the frontend will handle local identification of anonymous users through mechanisms like cookies or localStorage. This enhancement will allow users to create and manage up to three projects without requiring an account.