feat: add health check API and handle app configuration warnings

- Removed the old index.html file from the frontend build.
- Integrated a health check query in App component to verify app configuration.
- Display a warning alert if the app is not configured with AZURE_SUBSCRIPTION_ID.
- Updated API module to include health check endpoint.

.gitignore

@@ -12,12 +12,12 @@
 **/playground.py
 
 # Azure Secrets and Configuration.
-/.acr-pat
-/azure.env
+.acr-pat
+azure.env
 
 # MacOS Finder files
 **/.DS_Store
 
 # Node/React rewrite outputs
 **/node_modules
-/dist
+**/dist