fix: throw NotFoundException for unknown wallet reputation

[EmeditWeb]

Problem

In reputation.service.ts (line 79), if all data sources fail (Redis, Supabase, contract), the service returns a "poor" tier reputation (score=0) for a wallet that might not even exist on-chain.

What To Build

1. Throw NotFoundException if wallet has no on-chain score
2. Or return null/undefined and let caller handle
3. Log a warning when all data sources fail

Files To Touch

• src/modules/reputation/reputation.service.ts — line 79

Acceptance Criteria

• Non-existent wallets return 404 or explicit "not found"
• Log entry when all data sources fail
• Build passes

Mandatory Checks

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

[Chigybillionz]

Hi, I’ve reviewed this issue and I’m confident I can fix it. I’d like to take it on.