refactor: split large referralStore into focused slices

[nanaf6203-bit]

Summary

src/store/referralStore.ts mixes referral links, stats, leaderboards, notifications, errors.

Affected area

src/store/referralStore.ts

Expected behaviour

Split into useReferralLinks, useReferralStats, useLeaderboard, useReferralNotifications.

Acceptance criteria

• Backwards-compatible re-exports until consumers migrate.

[quickweb-stack]

@quickweb-stack has applied to work on this issue as part of the Stellar Wave Program's 6th wave.

I've reviewed the task and have a clear implementation plan. Looking forward to contributing with a quality PR.

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[Mirabel64]

@Mirabel64 has applied to work on this issue as part of the Stellar Wave Program's 6th wave.

Hello maintainer, can I work on this please

ℹ️ Repo Maintainers: To accept this application, review their application or assign @Mirabel64 to this issue.

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Congratulations, @Mirabel64! 🎉 Your application was accepted by the repo's maintainers, and the issue is due on June 30, 2026.

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[drips-wave]

This issue has been completed by @Mirabel64 as part of the Stellar Wave Program's 6th Wave 🥳

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