docs: added list of restricted envs and subdomains (medusajs#12810)

Author: shahednasser

www/apps/cloud/app/environments/page.mdx

@@ -68,6 +68,7 @@ To create a long-lived environment:
     - Select the branch you want to associate with this environment. For example, `staging`.
         - If you don't see the branch you want to use, refresh the page to load the latest branches from your repository.
     - Set the custom subdomain for the environment. All environments are subdomains of `medusajs.app`. So, if you set the subdomain to `staging-my-project`, the environment's URL will be `staging-my-project.medusajs.app`.
+        - Refer to the [Subdomain Restrictions](../projects/page.mdx#subdomain-restrictions) guide for reserved subdomains and restrictions.
 3. Once you're done, click the "Create" button.
 
 ![Side window with the form to create an environment](https://res.cloudinary.com/dza7lstvk/image/upload/v1749812846/Cloud/CleanShot_2025-06-13_at_14.04.53_2x_apb634.png)
@@ -186,6 +187,32 @@ Learn more in the [Logs guide](../logs/page.mdx).
 
 In an environment's "Settings" tab, you can manage the environment's variables.
 
+### Restricted Environment Variable Names
+
+The following environment variable names are reserved by Cloud and you can't use them in your environment:
+
+- `NODE_ENV`
+- `EXECUTION_CONTEXT`
+- `DATABASE_URL`
+- `REDIS_URL`
+- `MEDUSA_WORKER_MODE`
+- `PORT`
+- `K_SERVICE`
+- `K_CONFIGURATION`
+- `K_REVISION`
+- `K_CONTAINER_NAME`
+- `K_INTERNAL_POD_NAME`
+- `K_INTERNAL_POD_NAMESPACE`
+- `K_LOCAL_ADDR`
+- `K_PROTOCOL`
+- `SESSION_STORE`
+- `DYNAMO_DB_SESSIONS_TABLE`
+- `DYNAMO_DB_SESSIONS_HASH_KEY`
+- `DYNAMO_DB_SESSIONS_PREFIX`
+- `AWS_ACCESS_KEY_ID`
+- `AWS_SECRET_ACCESS_KEY`
+- `AWS_REGION`
+
 ### Add Environment Variables
 
 To add environment variables to an environment:

www/apps/cloud/app/projects/page.mdx

@@ -64,7 +64,7 @@ To create a project:
 
 6. In the next step, configure the project's settings:
     - Enter the name of the project.
-    - Enter a custom subdomain for the project. All projects are subdomains of `medusajs.app`. For example, if you enter `my-project`, the project will be accessible at `my-project.medusajs.app`.
+    - Enter a custom subdomain for the project. All projects are subdomains of `medusajs.app`. For example, if you enter `my-project`, the project will be accessible at `my-project.medusajs.app`. Refer to the [subdomain restrictions](#subdomain-restrictions) section for more details.
 
 ![The project settings step in the project creation flow with the settings filled in](https://res.cloudinary.com/dza7lstvk/image/upload/v1749741990/Cloud/CleanShot_2025-06-12_at_18.26.15_2x_kyxggl.png)
 
@@ -109,6 +109,18 @@ If you encounter any issues while creating a project:
 - [Check the build and runtime logs of the project's production deployment](../logs/page.mdx).
 - [Contact support for help](../support/page.mdx).
 
+### Subdomain Restrictions
+
+When you choose a subdomain for your project, it must be at least five characters long. It also can't be one of the following reserved subdomains:
+
+- `medusa`
+- `admin`
+- `staging`
+- `production`
+- `preview`
+- `development`
+- `proxy`.
+
 ---
 
 ## Access Deployed Project

www/apps/cloud/generated/edit-dates.mjs

@@ -1,8 +1,8 @@
 export const generatedEditDates = {
   "app/page.mdx": "2025-06-20T07:56:00.893Z",
   "app/organization/page.mdx": "2025-06-12T14:43:20.772Z",
-  "app/projects/page.mdx": "2025-06-19T14:17:06.679Z",
-  "app/environments/page.mdx": "2025-06-19T14:15:00.389Z",
+  "app/projects/page.mdx": "2025-06-24T11:17:17.668Z",
+  "app/environments/page.mdx": "2025-06-24T11:18:00.011Z",
   "app/deployments/page.mdx": "2025-06-19T14:14:31.740Z",
   "app/organizations/page.mdx": "2025-06-19T14:15:13.990Z",
   "app/notifications/page.mdx": "2025-06-17T12:29:18.819Z",