docs: improve alt of images (#12998)

* docs: improve alt of images

* fix vale errors

www/apps/book/app/learn/installation/page.mdx

@@ -45,7 +45,7 @@ After answering the prompts, the command installs the Medusa application in a di
 
 If you chose to install the storefront with the Medusa application, the storefront is installed in a separate directory named `{project-name}-storefront`.
 
-![Diagram showcasing an overview of the installation directories](https://res.cloudinary.com/dza7lstvk/image/upload/v1745856132/Medusa%20Resources/installation-dirs_x8jux4.jpg)
+![Directory structure overview after Medusa installation showing the main project folder containing the Medusa backend application and admin dashboard, alongside the separate storefront directory for the customer-facing Next.js application](https://res.cloudinary.com/dza7lstvk/image/upload/v1745856132/Medusa%20Resources/installation-dirs_x8jux4.jpg)
 
 ### Successful Installation Result
 
@@ -57,7 +57,7 @@ If you also installed the Next.js Starter Storefront, it'll be running at `http:
 
 You can stop the servers for the Medusa application and Next.js Starter Storefront by exiting the installation command. To run the server for the Medusa application again, refer to [this section](#run-medusa-application-in-development).
 
-![Diagram showcasing the server and applications running after successful installation](https://res.cloudinary.com/dza7lstvk/image/upload/v1745856706/Medusa%20Resources/success-overview_bj4pbt.jpg)
+![Post-installation running services overview: Medusa backend server and admin dashboard running on localhost:9000, Next.js Starter Storefront running on localhost:8000, with PostgreSQL database and other essential services active and ready for development](https://res.cloudinary.com/dza7lstvk/image/upload/v1745856706/Medusa%20Resources/success-overview_bj4pbt.jpg)
 
 ### Troubleshooting Installation Errors