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.

lib/canonicalStrategy.test.js

@@ -0,0 +1,57 @@
+import { describe, expect, it } from "vitest";
+import {
+  buildCanonicalQuery,
+  getEntityCanonical,
+} from "@/lib/getCanonicalUrl";
+
+const YASUJ_CITY_ID = 123;
+const ROOT_CITY_ID = 600;
+
+describe("buildCanonicalQuery — تصمیم M3-B", () => {
+  it("صفحهٔ ۲+ در canonical می‌ماند تا ایندکس‌پذیر بماند", () => {
+    expect(buildCanonicalQuery("?page=2")).toBe("?page=2");
+    expect(buildCanonicalQuery("?page=38")).toBe("?page=38");
+  });
+
+  it("صفحهٔ ۱ حذف می‌شود (URL متعارف بدون page)", () => {
+    expect(buildCanonicalQuery("?page=1")).toBe("");
+    expect(buildCanonicalQuery("")).toBe("");
+  });
+
+  it("فیلتر و sort و جستجو از canonical حذف می‌شوند", () => {
+    expect(buildCanonicalQuery("?specialty=x&gender=woman&sort=point&name=a")).toBe("");
+  });
+
+  it("page در کنار فیلترها فقط page را نگه می‌دارد", () => {
+    expect(buildCanonicalQuery("?specialty=x&page=3")).toBe("?page=3");
+  });
+});
+
+describe("getEntityCanonical — C1-b", () => {
+  it("موجودیت به دامنهٔ شهر خودش canonical می‌شود، نه دامنهٔ سرو‌کننده", () => {
+    expect(getEntityCanonical(YASUJ_CITY_ID, "/doctor/abc", "nobat724.com")).toBe(
+      "https://yasuj-nobat.ir/doctor/abc"
+    );
+  });
+
+  it("روی دامنهٔ خودِ شهر self-canonical است", () => {
+    expect(getEntityCanonical(YASUJ_CITY_ID, "/clinic/abc", "yasuj-nobat.ir")).toBe(
+      "https://yasuj-nobat.ir/clinic/abc"
+    );
+  });
+
+  it("شهر بدون دامنه → self-canonical (هرگز canonical شکسته)", () => {
+    expect(getEntityCanonical(999999, "/doctor/abc", "nobat724.com")).toBe(
+      "https://nobat724.com/doctor/abc"
+    );
+    expect(getEntityCanonical(null, "/doctor/abc", "tehran-nobat.ir")).toBe(
+      "https://tehran-nobat.ir/doctor/abc"
+    );
+  });
+
+  it("رکورد ریشه شهر نیست → self-canonical", () => {
+    expect(getEntityCanonical(ROOT_CITY_ID, "/doctor/abc", "yazd-nobat.ir")).toBe(
+      "https://yazd-nobat.ir/doctor/abc"
+    );
+  });
+});