🔒 Fix Insecure Randomness for Cryptographic Salt in App.tsx

[jason420247]

🎯 What:
Replaced insecure PRNG (Math.random()) with Web Crypto API (crypto.getRandomValues()) in TrinityKeystore.getVector() in App.tsx.

⚠️ Risk:
Math.random() produces predictable pseudo-random values which can allow attackers to predict cryptographic salts generated for Trinity Keystore vectors, compromising key security.

🛡️ Solution:
Utilized crypto.getRandomValues() via Uint32Array with fallbacks for browser (window.crypto) and Node (globalThis.crypto) environments to generate cryptographically secure salts.

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PR created automatically by Jules for task 3501896044810605655 started by @jason420247

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