Implement account regeneration in Settings view

[roninjin10]

Problem

The Settings view has a TODO at line 50 for regenerating test accounts. Confirming does nothing.

Current State

• Line 50: // TODO: Regenerate accounts
• Uses same confirmation dialog as reset
• Shows "Accounts regenerated" but nothing changes

Required Implementation

1. Add regenerateAccounts() method to Blockchain:
   • Generate 10 new random private keys
   • Derive addresses from private keys
   • Clear existing accounts from EVM database
   • Create new accounts with 10,000 ETH each
   • Update self.accounts list
2. Private key generation:
   • Use secure random bytes (std.crypto.random)
   • 32 bytes per key
   • Derive address via secp256k1 (or use evm's address derivation)

Key Files

• src/views/settings.zig:48-52 - Regenerate handler
• src/core/blockchain.zig - Need to add regenerateAccounts() method

Note

This is lower priority than other features. The hardcoded test accounts (Hardhat-compatible) are generally sufficient for development.

Acceptance Criteria

• Confirming regenerate creates 10 new accounts
• New private keys are cryptographically random
• Old accounts removed from EVM state
• New accounts have 10,000 ETH each
• Accounts view shows new accounts