feat: add footer component and complete Phase 2 static layout (Task 2.3)

dash_app/components/footer.py

@@ -0,0 +1,10 @@
+"""Page footer component."""
+from dash import html
+
+
+def make_footer():
+    """Build the page footer matching 01_nhs_classic.html."""
+    return html.Footer(
+        className="page-footer",
+        children="NHS Norfolk and Waveney ICB \u2014 High Cost Drugs Analysis",
+    )