Add Savings Product Subscription Limits

[Olowodarey]

Description:
Implement per-user and per-product subscription limits to prevent over-concentration and manage liquidity.

Acceptance Criteria:

• Add maxSubscriptionsPerUser to SavingsProduct
• Validation in subscribe endpoint
• Clear error messages when limit reached
• Admin override capability
• Waitlist integration when product is full
• Analytics on subscription capacity

[Elite-tch]

@Elite-tch has applied to work on this issue as part of the Stellar Wave Program's 3rd wave.

Please can i work on this issue

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

[NUMBER72857]

@NUMBER72857 has applied to work on this issue as part of the Stellar Wave Program's 3rd wave.

Kindly assign

ℹ️ Repo Maintainers: To accept this application, review their application or assign @NUMBER72857 to this issue.

[drips-wave]

Congratulations, @NUMBER72857! 🎉 Your application was accepted by the repo's maintainers, and the issue is due on March 30, 2026.

🧑‍💻 @NUMBER72857: Please resolve the issue such that the repo's maintainers have enough time to review your contribution before the due date. You'll earn Points for completing the issue on-time, which will make you eligible for a share of the Stellar Wave Program's reward pool.

Warning

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[drips-wave]

This issue has been completed by @NUMBER72857 as part of the Stellar Wave Program's 3rd Wave 🥳

😎 @NUMBER72857: You earned 200 Points for completing this issue! After the current Wave ends, you'll be eligible for a percentage of the Wave's reward pool based on the percentage of total points you've earned. Learn more here. You can also Leave a review to share your experience working on this issue.

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