UI foundations: PageHeader, StatTile, validated chart palette, registry primitives

- PageHeader + StatTile standardize the four header and three stat-tile
  variants found in the audit; Inicio and Salarios migrated as proof.
- chart tokens replaced with a teal-anchored categorical scale, CVD-
  ordered and validated (six checks, light + dark surfaces).
- Registry adds: empty, field, item, spinner, progress, toggle-group,
  input-group, popover, kbd (+ toggle dep).

Co-Authored-By: Claude Opus 4.8 (1M context) <noreply@anthropic.com>

frontend/src/components/page-header.tsx

@@ -0,0 +1,41 @@
+import type { LucideIcon } from "lucide-react";
+
+/** Standard page header: icon tile + title + optional subtitle on the left,
+ * page-level actions (period navigators, CSV, refresh…) on the right.
+ * Every page uses this — the breadcrumb in the shell header stays the only
+ * other place a page identifies itself. */
+export function PageHeader({
+  icon: Icon,
+  title,
+  subtitle,
+  actions,
+}: {
+  icon: LucideIcon;
+  title: string;
+  subtitle?: string;
+  actions?: React.ReactNode;
+}) {
+  return (
+    <div className="flex flex-wrap items-start justify-between gap-3">
+      <div className="flex items-center gap-3">
+        <div className="flex size-10 shrink-0 items-center justify-center rounded-lg bg-primary/10 text-primary">
+          <Icon className="size-5" aria-hidden />
+        </div>
+        <div>
+          <h1
+            className="text-2xl font-bold tracking-tight"
+            style={{ fontFamily: "var(--font-heading)" }}
+          >
+            {title}
+          </h1>
+          {subtitle && (
+            <p className="text-sm text-muted-foreground">{subtitle}</p>
+          )}
+        </div>
+      </div>
+      {actions && (
+        <div className="flex items-center gap-2">{actions}</div>
+      )}
+    </div>
+  );
+}