Use Shelly credentials in workflow callers

Map Shelly's repository secrets into the generic GitHub App reusable-workflow contract in the test callers and documented example.

Co-authored-by: Copilot App <223556219+Copilot@users.noreply.github.com>

Author: MariusStorhaug

.github/workflows/Workflow-Test-Default.yml

@@ -31,8 +31,8 @@ jobs:
     uses: ./.github/workflows/workflow.yml
     secrets:
       APIKey: ${{ secrets.APIKey }}
-      GitHubAppClientId: ${{ secrets.PSMODULE_CLIENT_ID }}
-      GitHubAppPrivateKey: ${{ secrets.PSMODULE_PRIVATE_KEY }}
+      GitHubAppClientId: ${{ secrets.SHELLY_CLIENT_ID }}
+      GitHubAppPrivateKey: ${{ secrets.SHELLY_PRIVATE_KEY }}
       TestData: >-
         {
           "secrets": {

.github/workflows/Workflow-Test-WithManifest.yml

@@ -31,8 +31,8 @@ jobs:
     uses: ./.github/workflows/workflow.yml
     secrets:
       APIKey: ${{ secrets.APIKey }}
-      GitHubAppClientId: ${{ secrets.PSMODULE_CLIENT_ID }}
-      GitHubAppPrivateKey: ${{ secrets.PSMODULE_PRIVATE_KEY }}
+      GitHubAppClientId: ${{ secrets.SHELLY_CLIENT_ID }}
+      GitHubAppPrivateKey: ${{ secrets.SHELLY_PRIVATE_KEY }}
       TestData: >-
         {
           "secrets": {

README.md

@@ -26,8 +26,8 @@ jobs:
   ProcessPSModule:
     uses: ./.github/workflows/workflow.yml
     secrets:
-      GitHubAppClientId: ${{ secrets.PSMODULE_CLIENT_ID }}
-      GitHubAppPrivateKey: ${{ secrets.PSMODULE_PRIVATE_KEY }}
+      GitHubAppClientId: ${{ secrets.SHELLY_CLIENT_ID }}
+      GitHubAppPrivateKey: ${{ secrets.SHELLY_PRIVATE_KEY }}
 ```
 
 This is a required contract for GitHub operations in the reusable workflow path; a GitHub App installation token is minted and used for those steps via `GH_TOKEN`, and `github.token` fallback is intentionally not used.