Add private-endpoint toggle and reduce what-if noise

[marcelloformica]

Summary

Add a usePrivateEndpoints toggle to the Bicep deployment, document the parameter set more clearly, and tighten the README.

Changes

• add usePrivateEndpoints to switch Storage Account and Function App private endpoints on or off
• keep the current deployment behavior when usePrivateEndpoints = true
• allow public reachability and skip PE subnet/DNS-zone dependencies when usePrivateEndpoints = false
• add explanatory comments to Bicep/parameters.dev.bicepparam
• streamline the README and document the new networking mode
• reduce ARM what-if noise with explicit Application Insights, blob service, and private endpoint defaults

Validation

• az bicep build --file Bicep/getavailability.bicep
• az deployment group validate --resource-group rg-getavail-itn-001 --parameters Bicep/parameters.dev.bicepparam
• az deployment group validate --resource-group rg-getavail-itn-001 --parameters Bicep/parameters.dev.bicepparam usePrivateEndpoints=false peSubnetId='' dnsZonesSubscriptionId='' dnsZonesResourceGroupName=''
• az deployment group what-if --resource-group rg-getavail-itn-001 --parameters Bicep/parameters.dev.bicepparam --only-show-errors

Notes

The what-if output improved, but some remaining diffs are still provider-managed or expression-based ARM noise rather than confirmed infrastructure drift.