feat: add deploy-dev workflow

.github/workflows/deploy-dev.yml

@@ -0,0 +1,36 @@
+name: Deploy
+on:
+  pull_request:
+    branches: [staging]
+    types: [closed]
+  push:
+    branches: [staging]
+  repository_dispatch:
+    types: [deploy-dev]
+  workflow_dispatch:
+
+jobs:
+  sync:
+    runs-on: ubuntu-latest
+    steps:
+      - id: checkout
+        name: Checkout
+        uses: actions/checkout@v3
+        with:
+          ref: dev
+
+      - id: pull-staging
+        name: Pull latest 'staging'
+        run: git pull origin staging
+
+      - id: diff-check
+        name: Check if 'dev' is behind 'staging'
+        run: git diff --exit-code origin/staging
+
+      - id: fast-forward
+        name: Fast forward 'staging' → 'dev'
+        run: git merge --ff-only origin/staging
+
+      - id: push-dev
+        name: Push latest 'dev'
+        run: git push --set-upstream origin dev