refactor: dedupe reports route, add PDF/CSV export tests, type frontend API client

[devin-ai-integration]

Summary

Quality-of-life improvements, no behavior changes:

Backend — routes/reports.js dedupe + constants
All three report endpoints repeated the same ID-validation → verify-client-ownership → fetch-work-entries pipeline. Extracted it into a shared loadClientReportData(req, res, entryColumns, onSuccess) helper, plus sumHours(workEntries) and buildExportFilename(clientName, extension) utilities (with JSDoc). PDF layout magic numbers are now named constants (PDF_PAGE_BREAK_Y, PDF_LINE_START_X/END_X, PDF_SEPARATOR_INTERVAL). Error responses and query shapes are unchanged.

Backend — tests for reports.js (64% → 93% stmt coverage)
Added tests for the previously uncovered PDF export success path: response headers/filename, title/totals text, No description fallback, page-break behavior when doc.y exceeds the threshold, and separator lines every 5 entries. All 164 tests pass.

Frontend — typed API client
ApiClient methods returned untyped response.data. Each method now declares its actual response shape (matching backend wrappers, e.g. getClients(): Promise<{ clients: Client[] }>, createWorkEntry(...): Promise<{ message: string; workEntry: WorkEntry }>), and request payloads use the existing CreateClientRequest/UpdateWorkEntryRequest etc. from types/api.ts. Also replaced an inline ad-hoc entry type in DashboardPage with WorkEntryWithClient, which surfaced (and fixes) a string | null vs string | undefined mismatch.

Verified: cd backend && npm test (164 passing), cd frontend && npx eslint src/ clean, npm run build succeeds.

Link to Devin session: https://partner-workshops.devinenterprise.com/sessions/29fe3065d49c499f80d84c81b6e88515

[devin-ai-integration]

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[sonarqubecloud]

Quality Gate passed

Issues
2 New issues
0 Accepted issues

Measures
0 Security Hotspots
0.0% Coverage on New Code
0.0% Duplication on New Code

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