Implement RecursiveTypeDecoder for nested data

[Marvelg256]

Description

Implement RecursiveTypeDecoder for nested data.

How It Was Done

• Added RecursiveTypeDecoder and TypeRef in crates/core/src/decode/recursive_decoder.rs.
• Updated scval_to_json to accept optional type metadata.
• Propagated contract type context through nested structs, enums, tuples, unions, options, results, vectors, and maps.
• Routed ReturnValueDecoder through the recursive dispatcher.
• Added coverage for nested struct → struct → enum/tuple decoding.

Issues Encountered (If Any)

The local Windows environment could not complete Cargo verification because rust-lld.exe access was denied. Formatting and git diff checks passed.

Related Issue

Closes #462

How It Was Tested

• rustfmt --check passed.
• git diff --check passed.
• Added a focused recursive nested-UDT unit test.
• Full Cargo check was attempted but blocked by the local linker permission error.

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[codeZe-us]

@Marvelg256 correct your PR description

[Marvelg256]

@Marvelg256 correct your PR description

corrected