test: comprehensive test suite for issues #415, #414, #413, #412 (#524)

* test: implement comprehensive tests for public invoice status page

Implements full test coverage for issue #415 - Dynamic Public Invoice Status Page.
Tests cover:
- PublicInvoiceView component rendering without authentication
- Payment status display and amount calculations
- Public API endpoint access and response validation
- Payment status polling at 10-second intervals
- Freighter wallet integration for payment submission
- OG meta tags for social sharing
- Server-side rendering performance
- Accessibility and UX features

Closes #415

Co-Authored-By: famvilianity-eng <famvilianity@gmail.com>

* test: implement comprehensive tests for invoice creation wizard

Implements full test coverage for issue #414 - Invoice Creation Guided Wizard Multi-Step.
Tests cover:
- Wizard structure with 4 distinct steps
- Step indicator and navigation
- Step 1: Basic Info validation and requirements
- Step 2: Recipients and splits validation
- Step 3: Payment Settings configuration
- Step 4: Review and submit functionality
- Session storage persistence and recovery
- Wizard toggle and flat form fallback
- useWizard hook functionality and state management

Closes #414

Co-Authored-By: famvilianity-eng <famvilianity@gmail.com>

* test: implement comprehensive tests for transaction explorer deep-link

Implements full test coverage for issue #413 - Onchain Explorer Deep-Link per Transaction.
Tests cover:
- TxExplorerLink component rendering and accessibility
- Explorer configuration for Stellar Expert, Stellarbeat, and StellarChain
- useExplorerPreference hook and localStorage persistence
- URL construction for mainnet and testnet networks
- Testnet fallback behavior for unsupported explorers
- Integration with Invoice View, Activity Feed, and Recipient History
- Explorer preference settings and immediate UI updates
- Keyboard navigation and ARIA labels
- Transaction filtering and display logic

Closes #413

Co-Authored-By: famvilianity-eng <famvilianity@gmail.com>

* test: implement comprehensive tests for batch payment approval queue

Implements full test coverage for issue #412 - Invoice Batch Payment Approval Queue.
Tests cover:
- Batch payment approvals page (/dashboard/approvals) and data table
- Invoice selection with support for select-all and shift-click range selection
- useBatchPayment hook for transaction assembly
- Stellar 100 operation limit handling and transaction splitting
- BatchConfirmModal component with full breakdown display
- Transaction submission and Freighter integration
- Atomic status updates and rollback error handling
- Support for multiple assets in batch payments
- User confirmation flow with step indicators
- @tanstack/react-table v8 integration
- Edge cases and validation scenarios

Closes #412

Co-Authored-By: famvilianity-eng <famvilianity@gmail.com>

Author: famvilianity-eng