feat: add canonical URL handling and entity quality checks

- Implemented canonical URL strategies for city-specific domains and entities.
- Added helper functions for domain and city resolution.
- Created tests for canonical URL generation and domain resolution.
- Introduced entity quality checks for doctors and clinics to ensure meaningful content.
- Developed unique introductory texts for listing pages to avoid duplicate content.
- Established robots.txt policies for listing pages to manage indexing based on user filters.
- Enhanced specialty content with dynamic introductions and FAQs to improve SEO.

app/blog/[slug]/page.js

@@ -4,7 +4,8 @@ import Layout from "@/components/layout/StLayout";
 import { notFound } from "next/navigation";
 import { fetchReq } from "@/lib/req";
 import { getStateInfo } from "@/lib/getStateInfo";
-import { getRequestOrigin } from "@/lib/getCanonicalUrl";
+import { getEntityOrigin } from "@/lib/getCanonicalUrl";
+import { extractEntityCityId, findCityById } from "@/lib/domainHelpers";
 import { safeJsonLd } from "@/lib/sanitize";
 import { normalizeBlog, imageUrl } from "@/helper";
 
@@ -38,11 +39,14 @@ export async function generateMetadata({ params }) {
     const description = rawText.slice(0, 160) || blog.title;
     const image = blog.image_url ? imageUrl(blog.image_url) : FALLBACK_IMG;
 
+    // C1-b — پست شهریافته به دامنهٔ همان شهر canonical می‌شود؛
+    // پست سراسری (بدون شهر) روی دامنهٔ جاری self-canonical می‌ماند.
+    const origin = await getEntityOrigin(extractEntityCityId(blog));
+
     return {
       title,
       description,
-      // محتوای بلاگ روی همه‌ی دامنه‌های شهری یکسان است — تجمیع اعتبار روی دامنه‌ی اصلی
-      alternates: { canonical: `https://nobat724.com/blog/${slug}` },
+      alternates: { canonical: `${origin}/blog/${slug}` },
       openGraph: {
         title,
         description,
@@ -59,18 +63,22 @@ export async function generateMetadata({ params }) {
         images: [image],
       },
     };
-  } catch {
+  } catch (error) {
+    console.error(`[blog/${slug}] generateMetadata failed:`, error);
     return {};
   }
 }
 
 async function Blog({ params }) {
   const { slug } = await params;
-  const origin = await getRequestOrigin();
 
   const blog = normalizeBlog(await getBlog(slug));
   if (!blog) notFound();
 
+  const blogCityId = extractEntityCityId(blog);
+  const blogCity = findCityById(blogCityId);
+  const origin = await getEntityOrigin(blogCityId);
+
   let relatedBlogs = [];
   const relatedResponse = await fetchReq(
     `${API_URL}/api/v1/blogs?page=1&limit=6`
@@ -90,6 +98,10 @@ async function Blog({ params }) {
           datePublished: new Date(blog.created * 1000).toISOString(),
         }),
         ...(blog.author && { author: { "@type": "Person", name: blog.author } }),
+        // پست شهریافته حوزهٔ جغرافیایی‌اش را اعلام می‌کند؛ پست سراسری این فیلد را ندارد.
+        ...(blogCity && {
+          spatialCoverage: { "@type": "Place", name: blogCity.name },
+        }),
       }
     : null;
 
@@ -120,7 +132,7 @@ async function Blog({ params }) {
         />
       )}
       <Layout>
-        <BlogPage blog={blog} blogs={relatedBlogs} />
+        <BlogPage blog={blog} blogs={relatedBlogs} cityName={blogCity?.name} />
       </Layout>
     </>
   );