`fafycat analytics breakdown` + `fafycat analytics variance`

[davidchris]

Parent

#26

What to build

Two date-range analytics commands grouped because they share input shape (date sugar) and output style (per-category aggregates).

• fafycat analytics breakdown calls AnalyticsService.get_category_breakdown. Optional --type income|spending|saving filter. Default range is the current month if no date flag is given (matches the existing service default).
• fafycat analytics variance calls AnalyticsService.get_budget_variance. Returns budget-vs-actual variance per category for the date range. Default range is the current month-to-date if no date flag is given.
• Both commands accept the full date sugar set defined in Date resolution module + fafycat analytics monthly #29.

Acceptance criteria

• fafycat analytics breakdown returns the current-month per-category breakdown.
• fafycat analytics breakdown --year 2025 --type spending filters to spending categories for 2025.
• fafycat analytics breakdown --start 2025-01-01 --end 2025-06-30 honors the explicit range.
• fafycat analytics variance returns the current-month variance.
• fafycat analytics variance --month 2026-04 returns April 2026 variance.
• fafycat analytics variance --year 2026 returns full-year variance.
• Stdout is JSON only; stderr is empty on the happy path.
• Tests are written before the implementation (red-green TDD).
• Subprocess integration tests cover: default range, year sugar, explicit --start/--end, --type filter for breakdown.

Blocked by

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