update: migration guide

docs/en/release-info/migration-guides/abp-10-1.md

@@ -47,6 +47,49 @@ In this version, we added password history/ user passkeys support to the [Identi
 
 > See [#23894](https://github.com/abpframework/abp/pull/23894) for more details.
 
+### Angular Version Upgraded to v21
+
+ABP now targets Angular v21 (up from v20). For existing Angular projects, apply these changes:
+
+- **TypeScript:** Update to `~5.9.0`
+- **main.ts:** Add `provideZoneChangeDetection()` to the bootstrap config:
+  ```ts
+    // angular/src/main.ts
+    bootstrapApplication(AppComponent, {
+        ...appConfig,
+        providers: [provideZoneChangeDetection(), ...appConfig.providers],
+    }).catch(err => console.error(err));
+  ```
+- **tsconfig.json:** Align with the new property formats to avoid build issues:
+  ```json
+    /* angular/tsconfig.json */
+    /* To learn more about this file see: https://angular.io/config/tsconfig. */
+    {
+      "compileOnSave": false,
+      "compilerOptions": {
+        "baseUrl": "./",
+        "outDir": "./dist/out-tsc",
+        "sourceMap": true,
+        "declaration": false,
+        "esModuleInterop": true,
+        "experimentalDecorators": true,
+        "moduleResolution": "bundler",
+        "importHelpers": true,
+        "skipLibCheck": true,
+        "target": "ES2022",
+        "module": "ES2022",
+        "lib": ["ES2022", "dom", "esnext.disposable"],
+        "paths": {},
+        "useDefineForClassFields": false
+      },
+      "angularCompilerOptions": {
+        "enableI18nLegacyMessageIdFormat": false
+      }
+    }
+  ```
+
+For more details, see the [Angular version reference](https://angular.dev/reference/versions#actively-supported-versions).
+
 ## PRO
 
 > Please check the **Open-Source (Framework)** section before reading this section. The listed topics might affect your application and you might need to take care of them.