🔒 Fix Insecure Randomness for Cryptographic Salt in App.tsx

[jason420247]

🎯 What: Fixed insecure randomness in TrinityKeystore.getVector() in App.tsx by using Web Crypto crypto.getRandomValues() instead of Math.random().

⚠️ Risk: Math.random() generates predictable values that are unsuitable for cryptographic salts or keys, allowing potential attackers to predict vector salts and compromise security.

🛡️ Solution: Replaced Math.random() with crypto.getRandomValues() using a cross-environment resolution (window.crypto / globalThis.crypto) with error handling if Web Crypto is unavailable.

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PR created automatically by Jules for task 10820299368151836128 started by @jason420247

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