Display banner in portal if App Insights / OTel has been incorrectly configured

#### What problem would the feature you're requesting solve? Please describe.

Currently, if App Insights is incorrectly configured (e.g., app doesn't have permission to send telemetry), the only way to find out is by going to the specific App Insights detector in Diagnose and Solve.

#### Describe the solution you'd like

Display a banner in the Azure Functions portal when a user navigates to an app's overview blade and the app has App Insights or OTel misconfigured.

#### Describe alternatives you've considered

Relying on customers' ability to do the following:
- navigate to the correct detector
- scroll to the bottom to see that it's getting a 401 when sending data
- understand what to do to solve the problem

#### Additional context
Add any other context or screenshots about the feature request here.

@RohitRanjanMS

The issue names no repository files, tests, or entry points. First establish whether the portal banner belongs in this host repository, then trace how App Insights or OTel configuration failures are exposed and how the portal overview can consume that signal. Done means a defined detection and banner behavior for the stated misconfiguration cases, with verification coverage identified.

Written by the indexing model from the issue text.