Implement subscription API rate limiting and usage metering

[Smartdevs17]

Description

Build a metering system that tracks API usage per subscription tier and enforces rate limits with soft warnings and hard caps.

Acceptance Criteria

• Usage metering per API key with hourly/daily/monthly counters
• Tier-based rate limits (free: 100/h, pro: 1000/h, enterprise: custom)
• Soft limit warning at 80% and 95% usage
• Hard limit enforcement with 429 response
• Usage analytics dashboard
• Automatic tier upgrade on sustained overuse

Technical Scope

• backend/services/
• src/store/subscriptionStore.ts
• Edge: usage spike handling, billing cycle reset, metering accuracy under load

[gidson5]

@gidson5 has applied to work on this issue as part of the Stellar Wave Program's 5th wave.

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[Itodo-S]

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

please let me work on this; I can handle it.

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[drips-wave]

Congratulations, @Itodo-S! 🎉 Your application was accepted by the repo's maintainers, and the issue is due on June 2, 2026.

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[drips-wave]

This issue has been completed by @Itodo-S as part of the Stellar Wave Program's 5th Wave 🥳

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