Implement subscription tax calculation and remittance system

[Smartdevs17]

Implement subscription tax calculation and remittance system

##Description

Context: Subscription payments may require tax calculation and remittance in various jurisdictions.

Current Limitation: No tax calculation exists in the system.

Expected Outcome: Implement tax system with configurable rates, automatic calculation, and reporting.

Acceptance Criteria

• Implement TaxConfig: rates by region, tax_type, remittance_schedule
• Add tax calculation per subscription transaction
• Support multiple tax types (sales tax, VAT, GST)
• Implement tax exemption handling
• Add tax reporting by jurisdiction
• Support tax remittance scheduling
• Implement reverse charge mechanism
• Create UI for tax configuration
• Write tests for tax calculations

Technical Scope

Files Likely Affected:

• contracts/tax/src/lib.rs - New tax module
• contracts/tax/src/calculation.rs - Tax calculations
• app/stores/taxStore.ts - Tax configuration
• app/screens/TaxSettingsScreen.tsx

APIs/Contracts Involved:

• calculate_tax(subscription_id: SubscriptionId, region: Region) -> TaxAmount
• get_tax_report(merchant_id: MerchantId, period: TimeRange, region: Region) -> TaxReport

Edge Cases to Consider:

• Tax rate changes mid-period
• Cross-border taxation
• Tax exemption validation

[UgoxyFavour]

@UgoxyFavour has applied to work on this issue as part of the Stellar Wave Program's 4th wave.

Can I work on this please

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

[christy-dev4]

@christy-dev4 has applied to work on this issue as part of the Stellar Wave Program's 4th wave.

I would love to work on this pls

ℹ️ Repo Maintainers: To accept this application, review their application or assign @christy-dev4 to this issue.