feat: SDK hashing

[cusma]

No description provided.

[Copilot]

Pull request overview

This PR introduces a new hashing module to the SDK, centralizing hash computation functions that were previously duplicated across test helpers. The changes refactor existing code to use the new module and add comprehensive test coverage for all hashing functionality.

Key Changes:

• Created new src/hashing.py module with hash computation functions (SHA-512/256, SHA-256, header/page/metadata hashing)
• Refactored tests/helpers/factories.py to use the centralized hashing module instead of local implementations
• Added extensive test coverage in tests/sdk/test_hashing.py with 973 lines of tests
• Enhanced type safety with explicit type annotations in test files

Reviewed changes

Copilot reviewed 7 out of 8 changed files in this pull request and generated 2 comments.

Show a summary per file

File	Description
src/hashing.py	New module implementing ARC-89 and ARC-3 hash computation functions
src/init.py	Exports new hashing functions in public API
src/codec.py	Replaced assert with ValueError for better error handling
tests/helpers/factories.py	Refactored to use centralized hashing module, removed duplicate implementations
tests/sdk/test_hashing.py	Comprehensive test suite for all hashing functions
tests/test_asset_metadata_factory.py	Added type annotations for better type safety
tests/smart_contract/test_arc89_get_metadata_b64_bytes_by_key.py	Added type annotations for better type safety

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