feat: Add pending status for Amazon orders awaiting shipment

[eshaffer321]

Summary

Orders that haven't shipped yet (no bank charges) are now tracked as "pending" instead of "failed". This provides clearer status reporting and ensures these orders are retried on subsequent syncs.

Problem: When an Amazon order is placed but hasn't shipped yet, there are no bank transactions to match. Previously this was logged as an ERROR and recorded as "failed", which was misleading since the order isn't actually broken - it's just not ready yet.

Solution:

• Added ErrPaymentPending sentinel error for orders awaiting shipment
• Amazon handler detects this and returns a skip with reason "payment pending"
• Orchestrator records as status="pending" (not "failed") and logs at INFO level
• Orders with pending status will be retried on subsequent syncs

Changes

• internal/adapters/providers/amazon/order.go - Add ErrPaymentPending error and improved GetFinalCharges() logic
• internal/adapters/providers/amazon/order_test.go - Add tests for pending scenarios
• internal/adapters/providers/amazon/provider_test.go - Update existing tests
• internal/application/sync/handlers/amazon.go - Detect pending and return skip
• internal/application/sync/orchestrator.go - Handle pending in handleResult()
• internal/application/sync/recording.go - Add recordPending() function
• web/src/app/(app)/orders/page.tsx - Add "Pending" to status filter dropdown

Test plan

• All Go tests pass (go test ./...)
• UI already supports pending status with amber badge
• Manual test: Run sync with an unshipped Amazon order - should show INFO log and pending status