feat(sdk-token): Add token allowance management methods to SDK

[Kevin737866]

Description

SDK methods for approve, allowance, transferFrom.

Acceptance Criteria

• approve(spender, amount); allowance(owner, spender)
• transferFrom(spender, from, to, amount)
• increaseAllowance, decreaseAllowance convenience methods
• Allowance event parsing
• Tests: approve, transferFrom, allowance query, insufficient allowance

Files to Modify

• sdk/src/tokenClient.ts
• sdk/src/types.ts

[tobiadewola41-eng]

@tobiadewola41-eng has applied to work on this issue as part of the Stellar Wave Program's 7th wave.

I would like to work on this issue now

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[0darkside0rbit-star]

@0darkside0rbit-star has applied to work on this issue as part of the Stellar Wave Program's 7th wave.

I would like to work on this issue please

ℹ️ Repo Maintainers: To accept this application, review their application or assign @0darkside0rbit-star to this issue.

[Paranoa-dev]

@Paranoa-dev has applied to work on this issue as part of the Stellar Wave Program's 7th wave.

Let me work on this for you
i can guarantee that i can delivery high level / high quality code before the deadline tomorrow

ℹ️ Repo Maintainers: To accept this application, review their application or assign @Paranoa-dev to this issue.

[Adecom16]

I'd like to work on this issue.
I'll implement the token allowance APIs (approve, allowance, transferFrom, increaseAllowance, and decreaseAllowance), add allowance event parsing, and include comprehensive tests covering approval, transfers, allowance queries, and insufficient allowance scenarios while keeping the SDK API consistent.