🔒 Fix Insecure Randomness for Cryptographic Salt in App.tsx

[jason420247]

🎯 What: Replaced Math.random() with crypto.getRandomValues() in TrinityKeystore.getVector inside App.tsx and added descriptive JSDoc documentation.

⚠️ Risk: Using Math.random() generates non-cryptographically secure pseudo-random values. Attackers could predict generated cryptographic salt vectors.

🛡️ Solution: Updated TrinityKeystore to use crypto.getRandomValues() with cross-environment resolution (window.crypto or globalThis.crypto) to generate secure random salts.

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PR created automatically by Jules for task 6179302996232183540 started by @jason420247

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