Set Unauthenticated as the authentication provider in the default Docker image config (#3248)

## Why make this change?

PR #3074 introduced `Unauthenticated` as the new default authentication
provider. The `dab-config.json` shipped in the Docker image
(quick-starter) was still referencing the old `Simulator` provider and
needs to be aligned.

## What is this change?

- Updated `dab-config.json` (root-level, copied into the Docker image
via `COPY dab-config.json /App/dab-config.json`) to use
`Unauthenticated` instead of `Simulator` as the authentication provider.

```diff
 "authentication": {
-  "provider": "Simulator"
+  "provider": "Unauthenticated"
 }
```

`Unauthenticated` treats all requests as anonymous without simulating
auth claims, which is the correct default for a quick-starter config.
`Simulator` was a development-only mode that would inject fake
authenticated identities.

## How was this tested?

- [ ] Integration Tests
- [ ] Unit Tests

The Docker image can start up with the updated default config values in
`dab-config.json`.

## Sample Request(s)

No API behavior change — this only affects the default provider in the
shipped config. Users connecting to the Docker image will have all
requests processed as the `anonymous` role by default.

<!-- START COPILOT ORIGINAL PROMPT -->



<details>

<summary>Original prompt</summary>

> 
> ----
> 
> *This section details on the original issue you should resolve*
> 
> <issue_title>Set Unauthenticated as the authentication provider in the
default config image</issue_title>
> <issue_description>- PR #3074 created the
Unauthenticated provider as the new default.
> - Switch to that in the `dab-config.json` that we will be shipping in
the docker image as a quick starter.</issue_description>
> 
> <agent_instructions>Adhere to formatting rules.
> Test by ensuring the docker image can start up with the default config
values in dab-config.json</agent_instructions>
> 
> ## Comments on the Issue (you are @copilot in this section)
> 
> <comments>
> </comments>
> 


</details>



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- Fixes #3247

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Co-authored-by: copilot-swe-agent[bot] <198982749+Copilot@users.noreply.github.com>
Co-authored-by: Aniruddh25 <3513779+Aniruddh25@users.noreply.github.com>
Co-authored-by: Souvik Ghosh <souvikofficial04@gmail.com>

Author: 3 people

dab-config.json

@@ -28,7 +28,7 @@
         "allow-credentials": false
       },
       "authentication": {
-        "provider": "Simulator"
+        "provider": "Unauthenticated"
       },
       "mode": "development"
     }