fix(ui): granular sleep sources, viewport-safe tour, one aligned settings language

A night with coarse apple-health samples next to granular watch data
showed only awake and asleep — the per-session source pick now prefers
the source that knows its stages. Tour popovers clamp into the
viewport, wrap their footer and fall back to a bottom sheet on narrow
screens. Settings and admin sections share one alignment rule — icon
column left, everything else flush on the content column — with neutral
header icons, no duplicated section titles under the shell heading, and
every select on the account-style idiom with a visible chevron. The
dashboard's customize icon matches insights, the target-settings link
leaves the home charts, and the mood heatmap adopts the damped fills
the other mood charts already use.

src/components/admin/assistant-section.tsx

@@ -107,10 +107,10 @@ export function AssistantSection() {
   return (
     <div className="bg-card border-border space-y-6 rounded-xl border p-6">
       <div className="flex items-center gap-2">
-        <Sparkles className="text-primary h-5 w-5" />
+        <Sparkles className="text-muted-foreground h-5 w-5" />
         <div className="text-lg font-semibold">{t("admin.assistant.title")}</div>
       </div>
-      <p className="text-muted-foreground text-sm">
+      <p className="text-muted-foreground pl-7 text-sm">
         {t("admin.assistant.description")}
       </p>