`fafycat analytics top`

[davidchris]

Parent

#26

What to build

Single subcommand fafycat analytics top that returns the largest spending transactions for a given month. Reuses AnalyticsService.get_top_transactions_by_month.

• Flags: --year YYYY (default current year), --month MM (default current month), --limit N (default 5, cap 50).
• Response shape mirrors the service: top transactions list, total spending for the month, and per-row percentage of total.

Acceptance criteria

• fafycat analytics top returns the current month's top 5 spending transactions as JSON.
• fafycat analytics top --year 2026 --month 4 returns April 2026 top transactions.
• fafycat analytics top --limit 10 returns the top 10.
• fafycat analytics top --limit 100 exits 2 with a usage error on stderr (cap is 50).
• fafycat analytics top --month 13 exits 2 with a usage error.
• Stdout is JSON only; stderr is empty on the happy path.
• Tests are written before the implementation (red-green TDD).
• Subprocess integration tests cover: defaults, explicit --year/--month, custom --limit, the over-cap error path, the invalid-month error path.

Blocked by

• Blocked by Date resolution module + fafycat analytics monthly #29