feat(coach): mount the drawer at the insights layout with a launch context

Promote the Coach drawer mount from the mother /insights page up to
/insights/layout.tsx so every routed sub-page can reach it. A new
CoachLaunchProvider exposes useCoachLaunch() for the hero strip,
suggested-prompt chips, and the seven sub-pages; the layout renders
the drawer beside the provider so navigation across Insights surfaces
no longer unmounts the conversation.

Each sub-page (blutdruck, gewicht, puls, stimmung, medikamente, bmi,
schlaf) mounts a new CoachLaunchButton that pins to the bottom on
narrow viewports and renders as an inline header action on lg+.

src/components/insights/coach-launch-button.tsx

@@ -0,0 +1,93 @@
+"use client";
+
+import { Sparkles } from "lucide-react";
+
+import { Button } from "@/components/ui/button";
+import { cn } from "@/lib/utils";
+import { useTranslations } from "@/lib/i18n/context";
+import { useCoachLaunch } from "@/lib/insights/coach-launch-context";
+
+/**
+ * v1.4.27 R3d MB4 — Coach launch button.
+ *
+ * Decision F: every routed Insights sub-page mounts this button so the
+ * Coach drawer (mounted at the layout root) is always reachable. The
+ * button renders as a sticky-bottom FAB on `<lg` viewports (so a phone
+ * user always sees it within thumb range) and as an inline header
+ * action on `lg+` (where the desktop drawer slides in from the right
+ * edge and the FAB would overlap the chart legend).
+ *
+ * The button is a thin wrapper around `useCoachLaunch()` — it only
+ * renders when the context provider is mounted (so dropping the button
+ * onto a non-Insights page is a no-op rather than a crash).
+ */
+export interface CoachLaunchButtonProps {
+  /** Optional override for the visual label. Defaults to the shared CTA. */
+  label?: string;
+  /** Optional prefill seed for the next Coach turn. */
+  prefill?: string;
+  /** Optional className passthrough for inline overrides. */
+  className?: string;
+}
+
+export function CoachLaunchButton({
+  label,
+  prefill,
+  className,
+}: CoachLaunchButtonProps) {
+  const { t } = useTranslations();
+  const launch = useCoachLaunch();
+
+  if (!launch) {
+    // The button only makes sense beneath the provider. Render nothing
+    // so the sub-page doesn't paint a dead control.
+    return null;
+  }
+
+  const accessibleLabel = label ?? t("insights.heroActionAskCoach");
+
+  return (
+    <>
+      {/* Sticky FAB on `<lg` viewports — pinned to the bottom-right so
+          the user's thumb always finds it. `bottom-20` clears the
+          mobile bottom navigation; `safe-area-inset-bottom` plus the
+          existing app shell padding keep it clear of the iOS home bar.
+          Hidden on `lg+` where the inline button below takes over. */}
+      <Button
+        type="button"
+        size="lg"
+        data-slot="coach-launch-fab"
+        onClick={() => launch.askCoach(prefill ?? null)}
+        aria-label={accessibleLabel}
+        title={accessibleLabel}
+        className={cn(
+          "fixed right-4 bottom-20 z-40 h-12 rounded-full px-4 shadow-lg",
+          "from-dracula-purple to-dracula-pink bg-gradient-to-br text-white",
+          "hover:from-dracula-purple/90 hover:to-dracula-pink/90",
+          "lg:hidden",
+          className,
+        )}
+      >
+        <Sparkles className="size-4" aria-hidden="true" />
+        <span>{accessibleLabel}</span>
+      </Button>
+      {/* Inline header-style action on `lg+`. Lives in the page body so
+          it picks up the sub-page layout's spacing instead of fighting
+          a sticky header overlay. */}
+      <Button
+        type="button"
+        variant="outline"
+        size="sm"
+        data-slot="coach-launch-inline"
+        onClick={() => launch.askCoach(prefill ?? null)}
+        className={cn(
+          "hidden h-10 gap-2 self-end lg:inline-flex",
+          className,
+        )}
+      >
+        <Sparkles className="size-4" aria-hidden="true" />
+        <span>{accessibleLabel}</span>
+      </Button>
+    </>
+  );
+}

src/components/insights/layout-coach-mount.tsx

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+"use client";
+
+import { CoachDrawer } from "@/components/insights/coach-panel/coach-drawer";
+import { useCoachLaunch } from "@/lib/insights/coach-launch-context";
+
+/**
+ * v1.4.27 R3d MB4 — bridge between the layout-level
+ * `<CoachLaunchProvider>` and the Coach drawer mount.
+ *
+ * The layout file is a server component (it lives next to other server
+ * components and feeds the `metadata` chain), so the actual `useState`
+ * + `<CoachDrawer>` consumer has to live inside a client island. This
+ * file is intentionally tiny — its only job is to read the context and
+ * render the drawer at the layout's mount site.
+ */
+export function LayoutCoachMount() {
+  const launch = useCoachLaunch();
+  if (!launch) return null;
+  return (
+    <CoachDrawer
+      open={launch.open}
+      onOpenChange={launch.setOpen}
+      prefill={launch.prefill}
+    />
+  );
+}