perf(contract): optimize privacy flag storage with SHA256 hashing

[EmmyKay0026]

Closes #163

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Hi @Cedarich, this PR is for issue #163 and optimizes the privacy flag storage in the Soroban contract by switching from a handle-based tuple key to a deterministic hashing algorithm (SHA256). This change aligns the privacy module with the contract's overall cryptographic commitment patterns while moving towards more compact storage keys.

`

Method	CPU Instructions	Memory (Bytes)	Key Size (Approx)
Baseline (Tuple)	8,191	734	~60 bytes
SHA256 (Optimized)	26,987	2,953	32 bytes

`

The increase in CPU instructions is a calculated trade-off to achieve smaller, deterministic storage keys which reduce long-term ledger fees.

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[Cedarich]

Resolve conflicts

[Cedarich]

Fix failing contract workflow

[Cedarich]

Please remove the following non-essential changes before merging:

• .turbo/cache/ files should not be committed.
• Revert the deletion of package-lock.json files in the root and sub-directories.
• Branch Integrity: Ensure that the merge does not accidentally delete directories like app/frontend or app/backend, which appeared to be missing in this branch's diff.

@EmmyKay0026

[EmmyKay0026]

Alright on it@Cedarich

[Cedarich]

Fix conflict