feat(portal-admin): audit dashboard — bar / donut / stacked-bar above the table

PR 3 of the charts chantier — closes the loop on ADR-0023 by
wiring the three starter components from #171 onto the /audit
page.

Three computed signals derive aggregations from the *current page's*
items (no new BFF endpoint — server-side stats land separately if
ever needed):

  * `dailyVolume` — events grouped by ISO date (YYYY-MM-DD).
  * `outcomeBreakdown` — counts per outcome.
  * `dailyByEventType` — flat (day, eventType, count) triples.

A new `<section class="charts">` renders above the existing filter
form, behind a `hasChartData()` guard so the section disappears
entirely on empty pages (no "0 events" donut, no half-rendered
bars). Each chart sits in a `.chart-tile`; the stacked-bar gets
`.chart-tile--wide` to span both grid columns since its legend
benefits from the extra horizontal space.

A `.charts-note` paragraph above the grid says explicitly that
the aggregations are "computed from the events currently loaded
on this page only" — honest disclosure of the per-page scope, no
misleading "all-time" framing.

Captions / descriptions / aria-labels live in plain English in the
template per ADR-0020's source-locale-only chrome posture. No new
i18n strings.

Bundle impact: the lazy `audit` chunk grows from ~4.4 KB to ~84 KB
gzip with the chart deps loaded — comfortable under [ADR-0017]'s
100 KB cap. The estimate in ADR-0023 was ~65 KB; Plot's full mark
set + d3-scale-chromatic interpolators add a bit more than
projected but still fit the budget.

Side tweaks:
  * `apps/portal-admin/project.json` bumps the `anyComponentStyle`
    budget from 5/6 KB to 6/8 KB to accommodate the charts grid
    SCSS (audit.scss lands at ~6.5 KB).
  * `apps/portal-admin/tsconfig.app.json` references the new
    `libs/shared/charts/tsconfig.lib.json` (auto-added by `nx
    sync` after the import in audit.ts).

Verification:
  * 57 portal-admin specs pass (was 54; +3 for the charts section
    rendering, the empty-page hide guard, and the donut center
    label binding).
  * `pnpm nx run-many -t lint test build --projects=portal-shell,
    portal-admin,shared-charts` — green.
  * Audit chunk gzip = 84 KB, under the budget.

apps/portal-admin/project.json

@@ -52,8 +52,8 @@
             },
             {
               "type": "anyComponentStyle",
-              "maximumWarning": "5kb",
-              "maximumError": "6kb"
+              "maximumWarning": "6kb",
+              "maximumError": "8kb"
             },
             {
               "type": "bundle",