Scope permissions to dispatch reusable workflow invokation (#11843)

# Introduction

Fixes `preview-dispatch` for external contributors such as this run 
FAILING =
https://github.com/twentyhq/twenty/actions/runs/14796579485/job/41545030774
NOW SUCCEEDING =
https://github.com/twentyhq/twenty/actions/runs/14797811684?pr=11827

.github/workflows/preview-env-dispatch.yaml

@@ -11,11 +11,6 @@ concurrency:
   group: ${{ github.workflow }}-${{ github.ref }}
   cancel-in-progress: true
 
-permissions:
-  contents: write
-  actions: write
-  pull-requests: read
-
 jobs:
   changed-files-check:
     uses: ./.github/workflows/changed-files.yaml
@@ -30,6 +25,10 @@ jobs:
 
   trigger-preview:
     needs: changed-files-check
+    permissions:
+      contents: write
+      actions: write
+      pull-requests: read
     if: needs.changed-files-check.outputs.any_changed == 'true' || contains(github.event.pull_request.labels.*.name, 'preview')
     timeout-minutes: 5
     runs-on: ubuntu-latest