chore: remove unused signing and auth token functions from crypto utils

[Danielodingz]

Closes #38

Description

This PR addresses dead code within the src/utils/crypto.ts file.
Previously, signWithPlatformKey() and generateChallengeToken() were defined but never utilized anywhere in the codebase. The Stellar signing logic is already correctly implemented and managed directly within src/stellar/signatures.ts.

This cleanup reduces code duplication and streamlines the utility module by safely removing these unused functions and their corresponding dead imports.

Changes Made

• src/utils/crypto.ts: Removed the signWithPlatformKey and generateChallengeToken functions.
• src/utils/crypto.ts: Cleaned up the unused imports for getPlatformKeypair and getNetworkPassphrase.

Impact

No functional changes or impact on existing workflows. Improves overall codebase maintainability by eliminating redundant and dead code, ensuring the Stellar signing logic remains centralized in src/stellar/signatures.ts.

[DeFiVC]

PR Review: chore: remove unused signing and auth token functions from crypto utils

Author: Danielodingz | Closes: #38 | CI: ✅ Green | Conflicts: ✅ None

Blocking Issues

None.

Code Issues

None. The removal is clean — both signWithPlatformKey and generateChallengeToken are confirmed unused (grep finds zero imports outside crypto.ts). The unused imports (getPlatformKeypair, getNetworkPassphrase) are correctly removed alongside the functions.

Minor Nits

• Entire crypto.ts may be dead code — After this removal, verifyStellarSignature and sha256Hash are the only remaining exports. Grep shows neither is imported anywhere in the codebase. Consider a follow-up to remove the entire file if these functions are also unused. This is outside the scope of #38.

What's Good

• Minimal, focused change — Only removes what the issue describes, no scope creep
• Correct cleanup — Functions, their JSDoc comments, and unused imports all removed together
• No functional impact — Confirmed by CI (Lint + Test both pass)
• Follows codebase conventions — Clean diff, consistent with existing style

Straightforward dead code removal. Approving."