feat(insights): add a retry affordance for failed briefing generation

Surface the generation-failure signal in the daily briefing card. When a
held briefing is shown but the last refresh failed, the footer states it
plainly and offers a retry that runs the existing explicit regenerate —
no warm-on-mount. When there is no briefing to fall back on, the empty
state reads "couldn't generate" with the same retry instead of the
generic "no briefing yet". The hint is suppressed when no AI provider is
configured, where that hint already owns the surface and a retry is
futile. New copy lands in all six locales.

src/app/insights/page.tsx

@@ -447,6 +447,12 @@ export default function InsightsPage() {
         // briefing is actually rendered (the empty-state path owns the
         // `noProvider` branch above).
         noProviderStale={briefingPayload !== null && !advisor.hasProvider}
+        // v1.25 — the last generation attempt failed. On a held briefing this
+        // adds a discreet "couldn't refresh — retry" footer hint; on an empty
+        // card it swaps the generic empty state for an honest "couldn't
+        // generate" one. Suppressed when no provider is configured (that hint
+        // owns the surface and a retry would be futile).
+        generationFailed={advisor.generationFailed && advisor.hasProvider}
         // v1.21.2 (A4) — server-resolved recall + forward-look off the dashboard
         // snapshot. Both strings are already localised; null leaves the card's
         // memory block unrendered.