chore(i18n): retire the now-orphan settings.kiInsights key

The dedicated card H2 was retired in the previous "drop AI prefix"
pass; the `settings.kiInsights` translation key it consumed has no
remaining call-site in source. Drop it from de / en / es / fr / it /
pl. Also update the message-thread test to the new "Insights
provider" copy.

src/components/insights/coach-panel/__tests__/message-thread.test.tsx

@@ -190,7 +190,10 @@ describe("<MessageThread>", () => {
         }}
       />,
     );
-    expect(html).toContain("could not reach an AI provider");
+    // v1.4.33 IW7 — copy rewritten from "AI provider" to "Insights
+    // provider" per the Marc-Voice rule (no "KI"/"AI" prefix in
+    // user-facing strings).
+    expect(html).toContain("could not reach an Insights provider");
   });
 
   it("hides the streaming bubble once its persisted twin lands by id", () => {
@@ -449,7 +452,10 @@ describe("<MessageThread>", () => {
       />,
     );
     expect(html).toContain("Daily limit reached; resets at 00:00 UTC.");
-    expect(html).not.toContain("could not reach an AI provider");
+    // v1.4.33 IW7 — fallback copy rewritten ("AI provider" -> "Insights
+    // provider"). Both old and new strings should be absent here when
+    // the budget-exceeded error takes precedence.
+    expect(html).not.toContain("could not reach an Insights provider");
   });
 
   it("surfaces the provider rate-limit copy for coach.provider.rate_limited", () => {