🔒 Fix Insecure Randomness for Cryptographic Salt in App.tsx

[jason420247]

🎯 What: Fixed insecure randomness vulnerability in TrinityKeystore.getVector() in App.tsx where Math.random() was previously used to generate cryptographic salts.

⚠️ Risk: Math.random() uses a pseudo-random number generator (PRNG) that is deterministic and predictable. Predictable salt generation compromises the cryptographic integrity of keys derived or parameterized by the vector, making generated salts subject to prediction or brute-force attacks.

🛡️ Solution: Replaced Math.random() with crypto.getRandomValues() via Web Crypto API (window.crypto or globalThis.crypto). Added explicit error throwing if a cryptographically secure RNG is unavailable in the execution environment.

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PR created automatically by Jules for task 11479224679304590343 started by @jason420247

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