[zklogin] use sha2 for public inputs hash, update vk

[joyqvq]

Updates FastCrypto zkLogin verification to match the V2 SHA-256 transcript implementation in zklogin-circuits.

1. V2 public-input hashing mirrors encodePublicInputsTranscript and computePublicInputsHash.
2. Fixed-width encoding and low-253-bit SHA-256 handling mirror src/lib/sha256.ts.
3. Updates the dev V2 verifying key from v2-main.
4. Preserves V1 verification and V2-first/V1-fallback rollout behavior.
5. Adds TypeScript fixture, boundary, validation, and live dev-prover tests.
6. (a rust sdk used by sui cli not needed for sui protocol change) V2 nonce and address-seed generation mirror src/lib/sha256Transcripts.ts.

[joyqvq]

rust functions -> typescript functions:

append_fixed_width_be → bigIntToFixedBytesBE
append_length_prefixed_bytes → encodeLengthPrefixedString
append_length_prefixed_padded_bytes → encodePaddedBytes
sha256_low_253 → sha256 + sha256DigestToField