[Backend] -- Implement Savings Milestone Badges

[Devsol-01]

Description:
Create badge system for savings milestones (first deposit, goal completion, streak maintenance) to encourage user engagement.

Acceptance Criteria:

• Design badge taxonomy
• Create badge earning logic
• Implement badge storage
• Add badge display API
• Create badge notifications
• Add badge sharing

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[Oluwasuyi-Timilehin]

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

Hello maintainers I'm a full stack developer experience in building scalable systems I can handle this perfectly if assigned

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

[Malcolm-Wander]

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

Hello maintainer, I’d love to work on this issue please thank you

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

[Vicistar-V]

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

I’d like to work on this issue because it contributes to improving the project's functionality, reliability, and overall user experience. I enjoy contributing to open-source projects and collaborating with maintainers to deliver clean, maintainable, and well-tested solutions.

I have experience working across frontend, backend, testing, API integration, debugging, and performance optimization tasks. I'm comfortable analyzing existing codebases, understanding requirements, implementing features or fixes, writing tests, and ensuring changes align with project standards and acceptance criteria.

My approach is to first understand the current implementation, identify the most maintainable solution, implement the required changes, add or update tests where necessary, and verify that everything works correctly before submitting a PR. I can communicate progress clearly and incorporate feedback quickly throughout the review process.

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

[Jumongweb]

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

Hi maintainer, i will like to solve this issue

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

[drips-wave]

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

🧑‍💻 @Oluwasuyi-Timilehin: 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

When opening a PR, please link it to this issue to ensure it gets tracked accurately. Points are awarded when this issue is marked as completed by the maintainer.

🤠 Repo maintainers: Please keep an eye on the contributor's progress and review their work before the due date. You can manage this issue, including adjusting its complexity and points, here.

🌊 Happy Wave 🌊