fix(frontend): three money formatters, mixed placeholders, left-aligned money columns #739

Summary

Money is formatted by three different functions with different rules, absent values use two different placeholders, and money columns are left-aligned without tabular numerals.

Where

Reviewed commit b50ca38:

• frontend/src/utils.ts:41 (0 decimals, separators)
• frontend/src/modules/savings-history.ts:335-342 (own formatCurrency with $1.23K, shadowing the import)
• frontend/src/recommendations.ts:1674,1693 ($${x.toFixed(n)}, so yearly prints $123456)
• frontend/src/dashboard.ts:282-287 (-- and — in one tile)
• frontend/src/styles/tables.css:13 (all th, td left-aligned; tabular-nums used twice)
• frontend/src/index.html:215-224 (Purchases stat cards start at $0.00)

Failure scenario

• Yearly savings on Opportunities print as $123456 with no separators.
• On the Purchases page "$19.52K" and "$216.92/mo" (compact, 2 decimals) sit above "$24,400" and "$2,560" (full, 0 decimals).
• Absent values use -- about 18 times and — about 35 times; Home empty shows four different empty values in four KPI tiles (green --, 0, bold —, green $0).
• Money columns are left-aligned, so digits do not line up for comparison.
  Verified live (mock API, static build) and in source.

User impact

All users comparing amounts. Unaligned, inconsistently formatted money makes columns hard to scan, and a $0 placeholder can read as a real zero.

Suggested fix

One formatMoney(v, {compact, digits}) on Intl.NumberFormat, one placeholder for absent values, and td.num { text-align: right; font-variant-numeric: tabular-nums } on every money and count column.

Screenshots

In the review fleet archive (/Users/cristi/.claude/agent-comms/review-fleet-20261008/screens/), NOT uploaded: home-empty-1280.png, purchases-full-1280.png.

Severity

Medium: inconsistent presentation of money across the app, no calculation error.

Related: #6 (generic UX backlog that lists this only in passing; not a duplicate).

Reviewer ID: VIS-11 (vis M5)
Found by the 2026-10-08 review fleet.