feat(FN-4100): refactor ci workflows to use reusable setup-node-pnpm compos

Refactors GitHub Actions workflow setup into a reusable composite action, consolidating repeated setup logic across CI, mobile, release, test-release, and version workflows (176 lines removed). Adds corresponding tests for the workflow configuration.

Fusion-Task-Id: FN-4100

.github/actions/setup-node-pnpm/action.yml

@@ -9,6 +9,14 @@ inputs:
     description: Arguments passed to pnpm install
     required: false
     default: "--frozen-lockfile"
+  registry-url:
+    description: Optional npm registry URL passed to actions/setup-node
+    required: false
+    default: ""
+  skip-install:
+    description: Set to 'true' to skip the pnpm install step; caller runs install themselves
+    required: false
+    default: "false"
 runs:
   using: composite
   steps:
@@ -20,7 +28,9 @@ runs:
       with:
         node-version: ${{ inputs.node-version }}
         cache: pnpm
+        registry-url: ${{ inputs.registry-url }}
 
     - name: Install dependencies
+      if: ${{ inputs.skip-install != 'true' }}
       shell: bash
       run: pnpm install ${{ inputs.install-args }}