Add IPFS pinning failure handling

[meshackyaro]

Description

IPFS pinning returns success even when pin fails. Silent failures accepted as success.

Component

Backend

Difficulty

🟡 Medium

Tasks

• Add proper error propagation from Pinata
• Verify pin status after pinning
• Throw errors on pin failure
• Add retry logic for transient failures
• Test with invalid credentials

Acceptance Criteria

• Pin failures throw errors
• Pin status verified
• No silent failures

Estimated Time

2 days