test: add hash resilience benchmark for ZK pipeline (#38)

[Tenerife-Q]

Added a standalone benchmark script to simulate how decentralized storage gateways (e.g., IPFS/NFT.storage) handle image uploads. Gateways often apply benign compression, such as stripping EXIF data or a 95% quality re-encode, to save bandwidth.

TL;DR: The current SHA-256 verification fails entirely under normal network conditions due to the avalanche effect. pHash effectively survives.

Here is the benchmark execution output:

Original SHA-256 : 509a84a2a30c7bd9e8914958a3dc447e7bc4a35cda5575d70383e659fee918dd
Original pHash   : c7c7383830c7c7c6

[Stage 2: Simulated Storage Gateway (95% JPEG Quality)]
New SHA-256      : 6d012dc328363b130b85fc2ea60626aaeec050a311d916433e66fceb60c7aecb
New pHash        : c6c7383830c7c7c7

[Stage 3: Verification Analysis]
SHA-256 Match    : False
                   (Strict hashing failed due to avalanche effect)
pHash Match      : True
Hamming Distance : 2
                   (Passed within configurable threshold <= 5)