feat(validation): Add circular type dependency check

[22Yash]

Problem:
Users can create a circular dependency between custom types (e.g., Type A references Type B, and Type B references Type A). This structure is invalid and cannot be correctly generated in a schema but was not being flagged as an issue.

Furthermore, an initial attempt to implement this failed due to a case mismatch between how custom type names are defined (type_a) and how they are referenced by fields (TYPE_A).

Solution:

1. Implemented Circular Dependency Check: Added a Depth First Search (DFS) algorithm within getIssues.js to detect cycles within the diagram.types graph.
2. Added Translation Key: Included the new translation key circular_type_dependency in en.js.
3. Fixed Casing Discrepancy (Name Normalization): Normalized all custom type names and references to uppercase within the DFS logic. This ensures the lookup works reliably regardless of the casing in the stored data, correctly identifying the circular reference.

Validation/Testing:
Created two custom types, type_A and type_B.

• type_A has a field referencing TYPE_B.
• type_B has a field referencing TYPE_A.

Expected Result (Achieved): The Issues panel now correctly displays "Issues (1)" and the message: "Circular type dependency detected in: type_A."

[vercel]

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