fix: maintain Services dropdown header from one canonical source

The site header / Services mega-dropdown was duplicated across two render
systems (Astro pages via Base.astro->nav.html, and ~80 pre-rendered static
public/**/index.html pages each embedding their own copy). They had drifted
into 5 different variants (missing 'New Carrier Setup', misplaced Healthcare
column, NEW vs FREE badges, em-dash encoding differences), so
dev.performancewest.net, the order pages, and the rest of the site disagreed.

- Make site/src/partials/nav.html the single source of truth (adopts the most
  complete variant).
- Add scripts/sync_nav.py to rewrite every static page's <nav> block from
  nav.html (idempotent; --check guards against drift in CI/deploy).
- Run the sync automatically in deploy.sh and scripts/deploy-dev.sh.
- Deprecate scripts/inject_healthcare_nav.py (now delegates to sync_nav.py).
- Neutralize the broken no-op SiteNav.astro component.

All 80 headers + the Astro-built order pages now render the identical dropdown.

deploy.sh

@@ -13,6 +13,14 @@ SERVICES="${@:-site api workers}"
 echo "=== Pulling latest from git ==="
 git pull origin main
 
+# Single source of truth for the site header: rewrite every static page's
+# <nav> block from site/src/partials/nav.html so the Services dropdown stays
+# identical across the static site, the Astro order pages, and dev. Idempotent;
+# does nothing if already in sync. (See scripts/sync_nav.py.)
+echo ""
+echo "=== Syncing canonical site header (Services dropdown) ==="
+python3 scripts/sync_nav.py
+
 echo ""
 echo "=== Building: $SERVICES ==="
 # ERPNext bakes the custom Frappe apps into its image, so they must be staged