docs: update env example and readme for user description

Add clarifying comment about DISPLAY_USER_DESCRIPTION in .env.example
Update README formatting and add note about home page cards effect

.env.example

···
 DISPLAY_USER_BANNER=false
 
 # Optional: Set to 'true' to display the user's description. Defaults to 'false'.
+# Note: This only affects the display of user descriptions on the home page cards.
 DISPLAY_USER_DESCRIPTION=false
 
 # Example DIDs:

README.md

···
     ```
 
     Example for controlling the display of the user description:
-    ```
-    DISPLAY_USER_DESCRIPTION=true
-    ```
+```
+DISPLAY_USER_DESCRIPTION=true
+```
+
+Note: `DISPLAY_USER_DESCRIPTION` only affects the display of user descriptions on the home page cards.
 
 4.  **Run the development server:**
     ```bash