Make cryptography browser/mobile ready

[mattgle]

Removes the two hard browser/mobile blockers so the package runs in browsers and React Native with no Node polyfills (no node:crypto, no Buffer).

• AES: node:crypto → @noble/ciphers
• Poseidon: circomlibjs WASM backend → pure-JS poseidon-lite
• EdDSA (BabyJubJub + Poseidon): circomlibjs buildEddsa → @iden3/js-crypto
• @noble/hashes bumped to v2; circomlibjs removed entirely

Wire formats and byte representations are unchanged and verified byte-identical to the previous implementation: AES ciphertext still decrypts, and Poseidon/EdDSA match the canonical circomlibjs reference vectors, so existing wallet keys and signatures continue to verify.

Poseidon and EdDSA are now synchronous, so the async init API (initPoseidon, initializeEddsa, initCircomlib, poseidonBuild) is removed.

[simonmasson]

Had a quick review and it seems to be OK. Would be better with noble/curves, but that's for later.

[bhflm]

looks good but I've found smth else

CryptographyErrorCode has two codes that we might need to removed bc they're not used anymore (```` 'EddsaNotInitialized' | 'PoseidonNotLoaded'```)

also there're a couple of functions that we might need to update from wallet-node?

I think README is outdated too

[mattgle]

looks good but I've found smth else

CryptographyErrorCode has two codes that we might need to removed bc they're not used anymore (```` 'EddsaNotInitialized' | 'PoseidonNotLoaded'```)

also there're a couple of functions that we might need to update from wallet-node?

I think README is outdated too

Yes we will need to make changes to wallet-node after this PR gets merged. Here's the PR for those changes railgun-reloaded/wallet-node#26