Add backend-generated sitemap with website manifest sync and nginx SEO proxy support.

Stores synced route config from /meshkee/sitemap-config.json, serves sitemap.xml and robots.txt per tenant, and invalidates cache on CMS writes.

Co-authored-by: Cursor <cursoragent@cursor.com>

docs/PROJECT_CONTEXT.md

@@ -262,6 +262,9 @@ All routes are prefixed with `/api/v1`.
 | POST | `/auth/verify-otp` | Verify OTP (marks cell verified; no tokens) |
 | POST | `/auth/handoff/consume` | One-time SSO ticket → tokens (customer → business dashboard) |
 | GET | `/tenants/:host` | Resolve business from domain (`specialProductsSource`, `enabledModules`, `homeCharts`, `ePayment`) |
+| GET | `/tenants/:host/sitemap.xml` | XML sitemap (static pages from synced manifest + published products/blogs/portfolios) |
+| GET | `/tenants/:host/robots.txt` | robots.txt pointing to apex `/sitemap.xml` |
+| POST | `/businesses/:id/website/sitemap/sync` | Import manifest from `GET https://{domain}/meshkee/sitemap-config.json` |
 | GET | `/tenants/:host/store-specials` | Active store specials (`source` is `product` or `store_item`) |
 | GET | `/tenants/:host/website/category-groups` | Homepage category rows |
 | GET | `/tenants/:host/website/brand-groups` | Homepage brand rows |