fix: prevent HTTP timeout in ledger confirmation polling

[EmeditWeb]

Problem

In blockchain.service.ts (lines 78-79), waitForLedgerConfirmation() polls 30 times with 2s delay = 60s total. If the network is slow, the HTTP request may timeout before that.

What To Build

1. Reduce polling to 20 attempts (40s max)
2. Add configurable timeout
3. Return early on confirmed status
4. Log warning if confirmation takes >30s

Files To Touch

• src/modules/blockchain/blockchain.service.ts — lines 78-79

Acceptance Criteria

• Max 40s polling duration
• Early return on confirmation
• Build passes

Mandatory Checks

• context/ files read
• npm run build passes
• PR references this issue