🔒 Fix Insecure Randomness for Cryptographic Salt in App.tsx

[jason420247]

🎯 What:
Replaced Math.random() in App.tsx (TrinityKeystore.getVector) with a cryptographically secure random number generator using crypto.getRandomValues().

⚠️ Risk:
Math.random() produces pseudorandom numbers that are statistically predictable. Using it to generate salts for cryptographic vectors in TrinityKeystore makes the generated keys vulnerable to prediction and replay/brute-force attacks.

🛡️ Solution:
Replaced Math.random() with Uint32Array and crypto.getRandomValues(), falling back to globalThis.crypto when necessary, ensuring cryptographically secure randomness across modern browser and Node environments.

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PR created automatically by Jules for task 3028078555293402696 started by @jason420247

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