feat: Implement activity-based wallet discovery with gap limit algorithm

[dirrrtyjesus]

This commit implements BIP-44 compliant activity-based wallet discovery to find ALL wallets with activity when importing from seed phrase, instead of just checking the first 20 addresses.

Changes

Core Implementation

• Add GAP_LIMIT (20) and MAX_DISCOVERY_ADDRESSES (1000) constants
• Implement gap limit discovery algorithm in activityDetection.ts
• Support batched parallel checking for performance optimization
• Add progress callback support for UI integration

Blockchain-Specific Activity Checkers

• Solana: Check SOL balance + transaction history
• Ethereum: Check ETH balance + nonce (tx count)
• Both include caching for efficiency

API Updates

• Export ethereumIndexed() for Ethereum path generation
• Add getStandardDerivationPath() helper function
• Update derivationPaths.ts to support activity-based discovery

Benefits

✅ Discovers ALL wallets with activity (not just first 20) ✅ BIP-44 standard compliant gap limit algorithm
✅ Efficient - stops after 20 consecutive empty addresses ✅ Performance optimized with batched parallel RPC calls ✅ Works for both Solana and Ethereum chains
✅ Comprehensive documentation included

Usage

When importing a seed phrase, the wallet will now:

1. Check addresses sequentially starting from index 0
2. Detect activity (balance or transactions)
3. Continue until finding 20 consecutive empty addresses
4. Return only wallets that have been used

See ACTIVITY_BASED_WALLET_DISCOVERY.md for detailed documentation.

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