i18n: localise the operator-disabled assistant notices

Four user-facing keys land in all six locale files so the
`<AssistantDisabledNotice>` component reads natively localised
copy:

  insights.coach.disabledByOperator
  insights.briefingDisabledByOperator
  insights.statusDisabledByOperator
  insights.correlationsDisabledByOperator

The Coach key nests under the existing `insights.coach.*` object;
the other three sit at the top of `insights.*` to avoid colliding
with the existing string-valued `insights.correlations` key.

The Health-Score explainer has no notice — its suppression is
silent on purpose so the bare delta digit still reads as a clean
KPI.

DE carries the full native phrasing; the established convention
for the other five locales (FR/ES/IT/PL/EN) keeps the user-facing
strings localised even where admin strings still default to
English.

src/components/insights/assistant-disabled-notice.tsx

@@ -32,9 +32,9 @@ interface AssistantDisabledNoticeProps {
 
 const SURFACE_LABEL_KEY: Record<AssistantDisabledSurface, string> = {
   coach: "insights.coach.disabledByOperator",
-  briefing: "insights.briefing.disabledByOperator",
-  insightStatus: "insights.status.disabledByOperator",
-  correlations: "insights.correlations.disabledByOperator",
+  briefing: "insights.briefingDisabledByOperator",
+  insightStatus: "insights.statusDisabledByOperator",
+  correlations: "insights.correlationsDisabledByOperator",
 };
 
 export function AssistantDisabledNotice({