feat(i18n): make Pulse Finances currency-configurable

[takanorinishida]

Finances tab hardcoded $ everywhere, so a non-USD install renders its own currency's amounts as if they were dollars (e.g. an outbound total of ¥2,120,000 shows as "$2.1M" — a 1000x misread, not just a symbol mismatch).

Changes

• LifeosPrincipal gains an optional currency field (ISO 4217), mirrored in the LIFEOS_CONFIG.toml scaffold. Unset defaults to USD, same pattern as the existing optional principal fields.
• observability.ts's /api/life/finances envelope now reports the resolved currency (fail-open to "USD" on any config error, matching loadYaml()'s existing contract).
• finances/page.tsx resolves a display symbol from that code (a small static table for the four currencies LifeOS ships sample data for, Intl.NumberFormat as best-effort fallback for anything else) and threads it through fmtHero/fmtExact and the trend chart's Y axis, replacing every hardcoded $.
• parseCurrencyCell() (INCOME.md/EXPENSES.md table parsing) now strips ¥/€/£/₩/₹ and the word "円" in addition to $, and recognizes 万/億 magnitude suffixes alongside the existing K/M — data additions to an existing table, not new branches. The obligations.yaml legacy-amount parser now reuses this same function instead of a narrower ad hoc regex that silently ignored magnitude suffixes.

Non-destructive

Currency unset (or explicitly "USD") renders byte-identical to before: the fallback table is checked before Intl, so the default symbol is the same "$" literal this page has always rendered, independent of the server's locale environment.

git diff main...HEAD | rg '^-' | rg -v '^---'

Every removed line is either a doc comment or the same original $-literal line now dispatching through currencySymbol/parseCurrencyCell — same original functions, no removed capability.

Verification

• Built and deployed to a live install with [principal] currency = "JPY" set; /api/life/finances returns currency: "JPY", and the tab renders ¥2.1M etc. instead of $2.1M.
• Standalone unit-style checks against parseCurrencyCell ($12,000, ~$40K, ¥100,000, ¥1万, 1.2億, ...) all match expected values.

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