Refactor payment processing to use strategy pattern for multi-chain support

[Smartdevs17]

Context

Payment processing needs strategy pattern for multi-chain.

Current Limitation

Payment logic is chain-specific.

Expected Outcome

• Chain-agnostic payment interface
• Strategy pattern for chains
• Pluggable token support
• Unified payment tracking

Acceptance Criteria

• Payment strategy interface
• Stellar payment strategy
• EVM payment strategy
• Strategy selection based on token
• Unified payment tracking
• Strategy testing with mocks
• Strategy configuration UI

Technical Scope

• src/services/walletService.ts - Wallet service
• contracts/ - Contract payments
• src/store/walletStore.ts - Wallet store
• src/screens/ - Payment UI

[bitcoindev817-hue]

@bitcoindev817-hue has applied to work on this issue as part of the Stellar Wave Program's 7th wave.

I'm a full-stack developer and I'd like to take this issue.
I understand the requirements and will follow the existing project structure, keep the implementation clean, and include proper tests where applicable.

ETA: 1–3 days (depending on scope)

ℹ️ Repo Maintainers: To accept this application, review their application or assign @bitcoindev817-hue to this issue.

[drips-wave]

Congratulations, @bitcoindev817-hue! 🎉 Your application was accepted by the repo's maintainers, and the issue is due on July 30, 2026.

🧑‍💻 @bitcoindev817-hue: 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 🌊

[drips-wave]

This issue has been completed by @bitcoindev817-hue as part of the Stellar Wave Program's 7th Wave 🥳

😎 @bitcoindev817-hue: 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.

🧑‍💻 Repo maintainers: How'd the contributor do? Leave a review to share your experience working with them.