Implement subscription payment retry with intelligent scheduling

[Smartdevs17]

Context

Failed payments need intelligent retry scheduling.

Current Limitation

Payment retry is basic with no intelligence.

Expected Outcome

• Intelligent retry scheduling
• Failure-aware retry logic
• Retry analytics
• Retry configuration

Acceptance Criteria

• Intelligent retry scheduling based on failure type
• Failure-aware retry logic
• Retry analytics (retry rate, success rate)
• Retry configuration per failure type
• Retry notifications
• Retry limits
• Retry documentation

Technical Scope

• backend/services/billing/dunning.ts - Dunning service
• contracts/subscription/src/ - Subscription contract
• src/store/subscriptionStore.ts - Subscription store
• src/screens/ - Retry management UI

[Dev-sandy1]

@Dev-sandy1 has applied to work on this issue as part of the Stellar Wave Program's 7th wave.

Good day. Can i work on these issue.

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Congratulations, @Dev-sandy1! 🎉 Your application was accepted by the repo's maintainers, and the issue is due on July 30, 2026.

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This issue has been completed by @Dev-sandy1 as part of the Stellar Wave Program's 7th Wave 🥳

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