Add subscription payment timeout and recovery handling

[Smartdevs17]

Description

Payment transactions can timeout or get stuck without recovery. Implement timeout detection and recovery mechanisms.

Acceptance Criteria

• Payment transaction timeout detection (configurable per chain)
• Transaction status recovery on timeout
• Automatic retry with higher gas on timeout
• Manual retry option for users
• Stuck transaction alerting
• Transaction health dashboard

Technical Scope

• contracts/subscription/src/lib.rs
• backend/services/
• Edge: chain reorg during timeout window, RPC node inconsistency, gas price spikes

[rindicomfort]

@rindicomfort has applied to work on this issue as part of the Stellar Wave Program's 5th wave.

I'd love to work on this

ℹ️ Repo Maintainers: To accept this application, review their application or assign @rindicomfort to this issue.