feat: Allow PublicKey for TokenCreateTransaction keys

[Adityarya11]

Description:

This PR updates TokenCreateTransaction to accept PublicKey objects for all key fields, in addition to the existing PrivateKey. This is a crucial feature to enable non-custodial transaction building.

With this change, an application (like an agent) can construct a transaction using a user's PublicKey, serialize it, and then return the bytes to the user for them to sign with their PrivateKey.

This implementation follows the exact pattern already established in TopicCreateTransaction.py, as suggested by the maintainer.

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Changes:

• Created a Key = Union[PrivateKey, PublicKey] type alias.
• Updated the TokenKeys dataclass to use the new Key type.
• Updated all set_*_key methods to accept the Key type.
• Updated the _to_proto_key helper to correctly handle both PrivateKey (by getting its public key) and PublicKey (by using it directly).

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Related issue(s):

Fixes #735
also fixes
#104

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Checklist

• Documented (Updated CHANGELOG.md)
• Tested (This is a direct import fix)

[exploreriii]

I think you need to unit and integration test the new functionality you've added - not just the existing functionality

For example
test if you can pass a public key and this will generate the token and convert to proto correctly
No tests for edge cases
I think we can expect ed2559 keys to have a problem with this method

[exploreriii]

missing edge cases please

[exploreriii]

@skurzyp-arianelabs requesting your opinion please

[skurzyp-arianelabs]

@exploreriii @Adityarya11 The implementation looks good to me, but I would recommend adding some testcases for ECDSA keys to make sure this implementation works fine for them too.
The full coverage would be using:

• ED25519 PrivateKey - present
• ED25519 PublicKey - present
• ECDSA PrivateKey
• ECDSA PublicKey

for setting the keys for the token.

Also, just to unify across the codebase I would recommend aligning the TopicCreateTransaction which currently accepts just the PublicKey. See: https://github.com/hiero-ledger/hiero-sdk-python/blob/main/src/hiero_sdk_python/consensus/topic_create_transaction.py Should i create an issue or can you handle it @exploreriii?

[exploreriii]

Thanks for your ideas. I'm working at the moment maybe @nadineloepfe or @manishdait are available, else i can create it likely in a few hours.

[exploreriii]

@manishdait created the issue, thank you so much

[exploreriii]

Hi @Adityarya11 I'll be releasing a new python sdk release soon -
if this PR is not done in time that's no problem, but note you will need to change your changelog entry and put it under a new unreleased section.
it may be easier to start fresh.
Thank you