CmdPal: Add URI protocol command to reload extension (#41445)

<!-- Enter a brief description/summary of your PR here. What does it
fix/what does it change/how was it tested (even manually, if necessary)?
-->
## Summary of the Pull Request

This PR introduces a new way to reload extensions externally and makes
the feature configurable in the settings UI.

- Adds a new URI protocol command `x-cmdpal://reload` → triggers an
extension reload
- Introduces a new "For Developers" section on the General settings page
- Includes an option to enable/disable the external reload feature
- **Note:** This change depends on the fix in #41344 to work correctly. 

Pictures? Pictures!

<img width="2312" height="1334" alt="image"
src="https://github.com/user-attachments/assets/6457ef5b-e75e-4118-86b7-7e20505527a3"
/>

<!-- Please review the items on the PR checklist before submitting-->
## PR Checklist

- [x] Closes: #40542 
- [ ] **Communication:** I've discussed this with core contributors
already. If the work hasn't been agreed, this work might be rejected
- [ ] **Tests:** Added/updated and all pass
- [ ] **Localization:** All end-user-facing strings can be localized
- [ ] **Dev docs:** Added/updated
- [ ] **New binaries:** Added on the required places
- [ ] [JSON for
signing](https://github.com/microsoft/PowerToys/blob/main/.pipelines/ESRPSigning_core.json)
for new binaries
- [ ] [WXS for
installer](https://github.com/microsoft/PowerToys/blob/main/installer/PowerToysSetup/Product.wxs)
for new binaries and localization folder
- [ ] [YML for CI
pipeline](https://github.com/microsoft/PowerToys/blob/main/.pipelines/ci/templates/build-powertoys-steps.yml)
for new test projects
- [ ] [YML for signed
pipeline](https://github.com/microsoft/PowerToys/blob/main/.pipelines/release.yml)
- [ ] **Documentation updated:** If checked, please file a pull request
on [our docs
repo](https://github.com/MicrosoftDocs/windows-uwp/tree/docs/hub/powertoys)
and link it here: #xxx

<!-- Provide a more detailed description of the PR, other things fixed,
or any additional comments/features here -->
## Detailed Description of the Pull Request / Additional comments

<!-- Describe how you validated the behavior. Add automated tests
wherever possible, but list manual validation steps taken as well -->
## Validation Steps Performed

src/modules/cmdpal/Microsoft.CmdPal.UI.ViewModels/SettingsViewModel.cs

@@ -38,6 +38,16 @@ public partial class SettingsViewModel : INotifyPropertyChanged
         }
     }
 
+    public bool AllowExternalReload
+    {
+        get => _settings.AllowExternalReload;
+        set
+        {
+            _settings.AllowExternalReload = value;
+            Save();
+        }
+    }
+
     public bool ShowAppDetails
     {
         get => _settings.ShowAppDetails;