🔒 Fix Insecure Randomness for Cryptographic Salt in App.tsx

[jason420247]

🎯 What:
Replaced insecure Math.random() usage in TrinityKeystore.getVector inside App.tsx with cryptographically secure random number generation using the Web Crypto API (window.crypto / globalThis.crypto with getRandomValues).

⚠️ Risk:
Math.random() produces PRNG sequences that are predictable and cryptographically weak. Using Math.random() for key generation or salt vectors allows potential attackers to predict generated salt values, undermining cryptographic isolation and security mechanisms.

🛡️ Solution:

1. Replaced Math.random() with Uint32Array filled via getRandomValues().
2. Safe fallback resolution checking window.crypto and globalThis.crypto to maintain compatibility across browser and Node.js environments.
3. Added explicit error handling when cryptographically secure randomness is unavailable.

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PR created automatically by Jules for task 7295765877815035340 started by @jason420247

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