Add typing, guards, and refactors across models & routers

[YoshihitoAso]

This pull request introduces several improvements and refactorings across the database models and contract interaction logic, focusing on type safety, error handling, and code clarity.

📌 Description

✅ Related Issues

• Close [Pyright] Fix type errors in contract models and issuer core support modules #1004

🔄 Changes

Type Annotations and Type Safety Improvements:

• Added or improved type annotations in many methods and class attributes, such as specifying return types and parameter types for async contract methods in personal_info.py and freeze_log.py.

Error Handling and Assertions:

• Introduced assertions and explicit error checks for required cryptographic keys and passwords before performing sensitive operations, such as decrypting keyfiles or encrypting personal information. This ensures that missing or misconfigured secrets are caught early with clear error messages.

Refactoring and Code Clarity:

• Used cast() from the typing module to clarify expected types when dealing with dynamic data (e.g., keyfiles, KMS results, and contract call returns), improving code readability and reducing runtime errors.
• Improved constructor logic in models such as IDXPersonalInfo to better handle initialization with optional arguments.
• Updated import statements for clarity and to use correct modules, such as importing decode_keyfile_json from eth_keyfile.keyfile.

📌 Checklist

• I have added tests where necessary.
• I have updated the documentation where necessary.

[github-actions]

Tests	Skipped	Failures	Errors	Time
2500	0 💤	0 ❌	0 🔥	14m 46s ⏱️