[FIN-04] Implement Financial Report

[kilip]

Description

Implement the financial report with yearly overview and drill-down capability.

Subtasks

• FIN-04-ST-01 Build yearly overview at /finance
• FIN-04-ST-02 Build monthly detail at /finance/[year]/[month]
• FIN-04-ST-03 UserRole gate: only treasurer, pastor, and executive-board can access
• FIN-04-ST-04 Display income/expense breakdown clearly

Acceptance Criteria

• FIN-04-AC-01 Yearly overview shows monthly income/expense summary
• FIN-04-AC-02 Drill-down to monthly detail works
• FIN-04-AC-03 Drill-down to individual transaction detail works
• FIN-04-AC-04 Unauthorized roles receive 403

Technical Notes

• Docs: PRD#64-financial-reports · TDD#83-permission-rules
• Screen spec: docs/screen.md → Financial Report, Monthly Period Detail

[kilip]

Walkthrough - Financial Reporting System (FIN-04)

Summary of implementation for #114:

1. Backend & Core Logic

• TransactionService: Implemented getYearlyReport and getMonthlyReport with type-safe grouping logic.
• Unit Tests: Full coverage for reporting logic with 100% type safety (no any).

2. UI Components (FSD)

• FinancialReportTable: Yearly overview table.
• MonthlyReportCollapsible: Monthly drill-down with per-category transaction details.
• Custom Accordion: Stable UI primitive using @base-ui/react.

3. Integration & Actions

• Server Actions: Robust error handling via ActionError.
• Pages: Integrated into Dashboard Finance and new Monthly Report details page.

Verification Results

• ✅ pnpm format & pnpm lint passed.
• ✅ pnpm typecheck passed.
• ✅ pnpm test passed.
• ⏩ E2E tests skipped per user request.

Closes #114