fix(phase3): description optional, restore nginx to host IP

- Make ledger description field optional (was required, caused 400)
- Revert nginx.conf back to 192.168.1.14:8090 (host IP, reliable)
- Keep docker-compose port mapping as 8090:8090
- Add $autoCancel:false to ledger/asset API calls

Co-Authored-By: Claude Opus 4.7 <noreply@anthropic.com>

frontend/src/api/ledgers.ts

@@ -7,7 +7,7 @@ interface CreateLedgerData {
   type: string
   amount: number
   category: string
-  description: string
+  description?: string
   relatedMembers?: string[]
   occurredAt: string
 }