critical: fix WalletState property mismatch in transaction-signer service

[EmeditWeb]

Problem

The transaction-signer.service.ts references:

• Line 110: walletState.publicKey — property does NOT exist on WalletState (the store uses address, not publicKey)
• Line 117: walletState.setSigning(true) — method does NOT exist on WalletState

User impact: Any attempt to sign a transaction will throw runtime errors. The transaction signing flow is completely broken.

Before Starting

Read: context/architecture-context.md

Root Cause

The service was written against an older version of the wallet store that had different property names.

What To Build

1. Fix publicKey → address in transaction-signer.service.ts
2. Add setSigning(isSigning: boolean) method to wallet.store.ts
3. Ensure isSigning state variable exists in the store
4. Write a test for the sign and broadcast flow

Files To Touch

• src/transactions/transaction-signer.service.ts — lines 110, 117 fix references
• stores/wallet.store.ts — add setSigning method

Acceptance Criteria

• transaction-signer.service.ts references correct property names
• wallet.store.ts has setSigning method
• Transaction signing flow works end-to-end
• All existing tests pass

Mandatory Checks

• context/ files read
• npm test passes
• PR references this issue