feat(insights,dashboard): empty states for first-run views

Closes the last two surfaces from the C5 audit.

- /insights — Top-level "no data" path replaces a bare "No data
  available" sentence with EmptyState (TrendingUp icon) + "Add a
  measurement" CTA into /measurements. The BMI section's
  height-not-set fallback gets a compact plain-variant EmptyState
  (Ruler icon) + "Open account settings" CTA instead of a single
  grey line that looked like a bug.
- / (dashboard) — When trendCards.length === 0 AND charts.length ===
  0 (a brand-new account with no data and the Getting-started
  checklist already dismissed) the dashboard rendered an empty
  0-px tile strip below the welcome banner. Now paints an
  EmptyState with the same quick-entry dialog wired to the CTA so
  the user can log their first measurement without leaving the page.

Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>

src/app/insights/page.tsx

@@ -7,7 +7,10 @@ import { useTranslations, useFormatters } from "@/lib/i18n/context";
 import { cn } from "@/lib/utils";
 import { Card, CardContent, CardHeader, CardTitle } from "@/components/ui/card";
 import { Badge } from "@/components/ui/badge";
+import { Button } from "@/components/ui/button";
+import { EmptyState } from "@/components/ui/empty-state";
 import { Progress } from "@/components/ui/progress";
+import Link from "next/link";
 import dynamic from "next/dynamic";
 
 const HealthChart = dynamic(
@@ -809,10 +812,20 @@ export default function InsightsPage() {
   }
 
   if (!data) {
+    // v1.4.15 phase-C5: replace bare "no data" text with EmptyState +
+    // CTA into /measurements so the user has a single-click path out
+    // of the empty insights view.
     return (
-      <div className="text-muted-foreground py-20 text-center">
-        {t("common.noData")}
-      </div>
+      <EmptyState
+        icon={<TrendingUp className="size-6" />}
+        title={t("insights.emptyTitle")}
+        description={t("insights.emptyDescription")}
+        action={
+          <Button size="sm" asChild>
+            <Link href="/measurements">{t("insights.emptyAddMeasurement")}</Link>
+          </Button>
+        }
+      />
     );
   }
 
@@ -1491,7 +1504,24 @@ export default function InsightsPage() {
             valueBands={bmiBands}
           />
         ) : (
-          <p className="text-muted-foreground text-sm">{t("common.noData")}</p>
+          // v1.4.15 phase-C5: explicit empty state when the user
+          // hasn't set a height yet — without it the BMI card looked
+          // broken. Plain variant so the dashed border doesn't double
+          // up inside the section card.
+          <EmptyState
+            variant="plain"
+            size="compact"
+            icon={<Ruler className="size-5" />}
+            title={t("insights.bmiEmptyTitle")}
+            description={t("insights.bmiEmptyDescription")}
+            action={
+              <Button variant="outline" size="sm" asChild>
+                <Link href="/settings/account">
+                  {t("insights.bmiEmptyAction")}
+                </Link>
+              </Button>
+            }
+          />
         )}
 
         <InsightStatusCard

src/app/page.tsx

@@ -24,6 +24,7 @@ import {
 import type { DataSummary as DataSummaryType } from "@/lib/analytics/trends";
 import dynamic from "next/dynamic";
 import { Button } from "@/components/ui/button";
+import { EmptyState } from "@/components/ui/empty-state";
 import {
   Dialog,
   DialogContent,
@@ -950,6 +951,35 @@ export default function DashboardPage() {
 
         charts.sort((a, b) => a.order - b.order);
 
+        // v1.4.15 phase-C5: dashboard fully-empty state. When no tile
+        // and no chart has data the dashboard would otherwise paint a
+        // 0-px tile strip with the welcome banner above it — visually
+        // looked like a half-broken page. Render an EmptyState that
+        // re-uses the existing quick-entry dialog so the user has a
+        // single click into "Log measurement" without leaving the page.
+        // The GettingStartedChecklist above renders its own self-gated
+        // surface for very-new accounts; this empty state covers the
+        // case where the checklist has been dismissed but no data was
+        // logged afterwards.
+        if (trendCards.length === 0 && charts.length === 0) {
+          return (
+            <EmptyState
+              icon={<Activity className="size-6" />}
+              title={t("dashboard.emptyTitle")}
+              description={t("dashboard.emptyDescription")}
+              action={
+                <Button
+                  size="sm"
+                  onClick={() => setQuickEntryDialog("measurement")}
+                >
+                  <Plus className="mr-1 h-4 w-4" />
+                  {t("dashboard.emptyAddMeasurement")}
+                </Button>
+              }
+            />
+          );
+        }
+
         return (
           <>
             {/* v1.4: dashboard tiles are *always* a single row.