feat: add work order dropdown and receipt linking to expense detail edit (#235)

[daveharmswebdev]

Summary

Implements Story 16.4 — Expense-WorkOrder & Expense-Receipt Linking (Issue #235).

Allows property owners editing an expense at /expenses/:id to:

• Link a work order via a dropdown filtered by the expense's property (AC1), which clears and reloads when the property changes (AC2)
• Link an unprocessed receipt via an inline thumbnail picker (AC3)
• Unlink a receipt from edit mode, returning it to the unprocessed queue (AC4)

Changes

Backend (new)

• LinkReceiptToExpense.cs — MediatR command + handler that sets both FK sides of the 1:1 receipt-expense relationship (expense.ReceiptId, receipt.ExpenseId) and marks receipt.ProcessedAt = UtcNow. Follows the Story 15.4 UnlinkReceipt pattern in reverse. Includes property sync when receipt has no property.
• LinkReceiptToExpenseValidator.cs — FluentValidation: ExpenseId and ReceiptId must be non-empty GUIDs.
• ExpensesController.cs — New POST /api/v1/expenses/{id}/link-receipt endpoint returning 204/404/409. Includes LinkReceiptRequest record.

Frontend (modified)

• expense-detail.component.ts — Added work order dropdown (workOrderId form control, loadWorkOrders(), propertyId valueChanges listener for AC2 reset), receipt picker UI (thumbnail grid, loadUnprocessedReceipts() via ApiClient, linkReceipt() method, unlink button in edit mode). Added SlicePipe for description truncation.
• expense.service.ts — Added linkReceipt(expenseId, receiptId) method (manual, pending NSwag regen).
• expense-detail.component.spec.ts — Fixed TEA red-phase test by providing mock unprocessed receipts to component signal.

Tests & E2E (pre-created by TEA agent)

• LinkReceiptToExpenseHandlerTests.cs — 9 unit tests: happy path (both FKs, ProcessedAt, property sync, SaveChanges) + error cases (404 expense/receipt, 409 conflict already linked/processed)
• LinkReceiptToExpenseValidatorTests.cs — 3 validation tests
• expense-detail.component.spec.ts — 10 new component tests (5 work order dropdown AC1/AC2, 5 receipt linking AC3/AC4)
• expense-linking.spec.ts — 7 E2E acceptance tests (require full stack for green)
• expense-detail.page.ts — Page object with receipt linking locators and methods

Sprint artifacts

• Story status → dev-complete
• Sprint status YAML updated

Test Results

Suite	Result
Backend (dotnet test)	1,484 / 1,484 pass (941 Application + 85 Infrastructure + 458 API)
Frontend (npm test)	2,420 / 2,420 pass
TypeScript compilation	0 errors
E2E (acceptance)	7 tests written, require running backend for validation

API Design

POST /api/v1/expenses/{id}/link-receipt
Body: { "receiptId": "guid" }
204 — Receipt linked successfully
404 — Expense or receipt not found
409 — Expense already has receipt / receipt already processed

Test plan

• Backend unit tests pass (dotnet test --filter "LinkReceiptToExpense")
• Frontend component tests pass (npm test from /frontend)
• TypeScript compiles with zero errors
• E2E: Navigate to expense detail → Edit → see work order dropdown with property's work orders
• E2E: Change property in edit form → work order dropdown clears and reloads
• E2E: Edit expense with no receipt → see receipt picker with unprocessed thumbnails
• E2E: Select receipt thumbnail → click "Link Selected Receipt" → success snackbar
• E2E: Edit expense with linked receipt → see "Unlink Receipt" button (not picker)
• Verify NSwag client regeneration after merge (npm run generate-api)

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