refactor(i18n): shorten the five descriptions the gate could not see

The gate the diet shipped with matched `<SettingsCardHeader` in three
component folders. That is not where every card description lives, so five
real ones were outside its reach — including the full backup's, which the
sweep's own shortlist had named and which stayed at 351 German characters
across three sentences while the guard reported zero violations.

Two ways in were missing. A card header can sit in a folder the walk never
entered (`labs`), and a description can be FORWARDED to the header by a shell
— `ExportCardShell`, `ImportCardShell` — where the prop is on the shell's tag,
not the header's. The gate now matches both, over seven roots, and the
"finds what it is meant to check" floor moved with it.

`SubPageShell` is deliberately not included, with the reason written at the
list: its description renders as `text-foreground text-sm`, the body tier,
where the standards allow prose. Gating it would enforce a rule §3 does not
make for that tier.

The five, all six locales:

- full backup — the twelve-item enumeration was the description. It is now
  the card's opening body paragraph, where a list of what is in the file
  belongs; the description is one sentence.
- local OCR — the how-it-works sentence stays in the slot; "less accurate,
  review every value" is safety copy and reads foreground in the body.
- CSV import, dose-history import — second sentence to the body.
- the ECG page — the "does not interpret the waveform" claim gets its own
  paragraph rather than riding the page explainer.

Proven by reverting the full backup's text: the widened gate reports it as
both two sentences and over length, at the call site, in both languages. The
old gate could not see the key at all.

src/app/insights/ecg/page.tsx

@@ -76,6 +76,11 @@ export default function InsightsEcgPage() {
       title={t("insights.ecg.sectionTitle")}
       description={t("insights.subPage.ecgDescription")}
     >
+      {/* What the app does and does not claim about a trace. Its own
+          paragraph, so the page explainer above stays one sentence. */}
+      <p className="text-muted-foreground text-sm">
+        {t("insights.subPage.ecgDisclaimer")}
+      </p>
       <EcgSection enabled={isAuthenticated} hideHeading />
     </SubPageShell>
   );