fix(reports): make a drill-down explain the figure that opened it

[KenTaniguchi-R]

Closes #144.

Clicking a spending row opened a sheet whose total disagreed with the row, for three separate reasons.

1. The sheet summed only the page it had

drill-down-sheet.tsx added up rows, which is capped at DRILL_DOWN_LIMIT = 50. Any category with more transactions than that showed a total short of the row above it, silently.

getDrillDownTransactions now returns total and matchCount computed over the whole matching population. The page is still 50 rows and now says so: "Showing the most recent 50 of 120".

2. The list was a different population from the figure

The query passed category + dates only, so a list explaining a spending number also contained transfers, pending rows and refunds — exactly the rows that figure excludes.

It now builds on spendingBaseConditions (the definition #142 made canonical), or incomeBaseConditions when an income node was clicked. Both are exported from spending-helpers rather than restated at the call site. The income rule matches the Sankey's income nodes and the Income vs Expense table — deliberately not the Total Income tile, whose extra uncategorized credits are the open gross-vs-net question in #146.

3. The sheet and the page disagreed about the date range

The page resolves its range from the preset; the sheet read useSearchParamFilters().dateRange, which falls back to 2000-01-01→today. On a bare /reports the URL carries no dates at all, so the tab showed three months while the drill-down queried all time — a $1,891.26 Groceries row opening a $3,746.58 sheet.

The resolved dateFrom / dateTo / accountIds are now passed down from the page through ReportTabs to each tab, so the two can no longer diverge. This also fixes the account filter, which the drill-down previously ignored entirely.

Refactor

getTransactions keeps its filter-shaped API. The page fetch underneath is extracted as fetchTransactionPage(householdId, conditions, …) so the report query can supply its own conditions without duplicating the split/row enrichment.

Tests

New tests/integration/report-drill-down.test.ts (6 tests), each pinning the drill-down against the tab figure that opens it:

• total equals the Spending tab row
• lists only the transactions the figure counted (refund, pending, transfer, paired leg and out-of-range rows all excluded)
• total covers all 120 matches while the page holds 50
• uncategorized drill-down matches its Spending row
• honours the account filter
• income drill-down total equals the Cash Flow income node

Verification

Full suite: 1061 passed, 1 failed — investment-queries.test.ts > returns dayChange from holdings_history, which is pre-existing hardcoded-date rot on clean main.

Checked live against demo data: Groceries reads $1,891.26 / 24 transactions on both the row and the sheet; Cash Flow's Salary node reads $23,100.00 / 6 on both.

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