feat(demo): transaction builder

[m-kus]

TL;DR

Added a transaction builder interface that allows users to compose and execute multiple privacy pool operations in a single transaction, alongside the existing individual action buttons.

What changed?

• Added a new TransactionBuilder component with support for batching deposit, transfer, withdraw, surplus, and invoke operations
• Implemented useTransactionBuilder hook to handle batch transaction execution with automatic approval and proof generation
• Added a view toggle between "Actions" and "Builder" modes in the action panel
• Converted account selector from dropdown to tab-based interface for better UX
• Added a register operation to both action panel and transaction builder
• Enhanced styling with new CSS classes for tabs, builder interface, and operation management
• Implemented localStorage persistence for active account selection
• Removed the ability to add new accounts dynamically from the UI

How to test?

1. Switch between "Actions" and "Builder" tabs in the right panel
2. In Builder mode, add multiple operations (deposits, transfers, withdrawals) and execute them as a batch
3. Try the new Register button in Actions mode
4. Verify account selection persists across page refreshes
5. Test the new tabbed account selector interface

Why make this change?

The transaction builder enables more complex privacy pool interactions by allowing users to compose multiple operations into a single transaction, which is more efficient and provides better privacy guarantees. The UI improvements make account management more intuitive and provide a cleaner interface for both simple actions and advanced batch operations.

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This change is 

[m-kus]

• feat(demo): allow to edit class hash #583
• feat(demo): add subsystem health indicators to explorer #600
• feat(demo): group notes by channel into card layout #584
• feat(demo): transaction builder #580 👈 (View in Graphite)
• feat(demo): privacy pool deployment #568
• feat(demo): starknet integration demo explorer #556
• fix(e2e): add declare-class script and fix outgoing sync #555 : 1 other dependent PR (#533 )
• feat(sdk): proving service integration #538 : 2 other dependent PRs (#539 , #553 )
• main

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