Feature: Add transaction status tracking and history

[Mosas2000]

Summary

After submitting a transaction (stake, vote, create-proposal, execute), users see a success or error message but have no way to track the transaction status or view their transaction history within the application.

Recommended Implementation

1. Add a transaction history panel that shows all user transactions
2. Poll the Stacks API for transaction confirmation status
3. Show pending, confirmed, and failed states with visual indicators
4. Link each transaction to the Stacks Explorer
5. Show estimated confirmation time
6. Update proposal data automatically when related transactions confirm

Impact

Medium - Transaction visibility is essential for blockchain application trust.