chore: add CD workflow template and point spawn action to main (#19430)

## Summary

- Adds reusable composite GitHub Actions for Twenty app deployment:
- `.github/actions/deploy` — builds and deploys to a remote instance
(`api-url`, `api-key` inputs)
- `.github/actions/install` — installs/upgrades on a specific workspace
(`api-url`, `api-key` inputs)
- Adds a `cd.yml` CD workflow that calls both actions in sequence. The
workflow:
  - Deploys on push to `main`
  - Can be triggered from a PR by adding a `deploy` label
- Configures a named remote via `TWENTY_DEPLOY_URL` env var and
`TWENTY_DEPLOY_API_KEY` secret
- Applied to: `create-twenty-app` template, `postcard` example,
`hello-world` example
- Updates the `spawn-twenty-app-dev-test` action ref from
`@feature/sdk-config-file-source-of-truth` to `@main` in all `ci.yml`
files

packages/twenty-apps/examples/hello-world/.github/workflows/cd.yml

@@ -0,0 +1,42 @@
+name: CD
+
+on:
+  push:
+    branches:
+      - main
+  pull_request:
+    types: [labeled]
+
+permissions:
+  contents: read
+
+env:
+  TWENTY_DEPLOY_URL: http://localhost:3000
+
+concurrency:
+  group: cd-${{ github.ref }}
+  cancel-in-progress: true
+
+jobs:
+  deploy-and-install:
+    if: >-
+      github.event_name == 'push' ||
+      (github.event_name == 'pull_request' && github.event.label.name == 'deploy')
+    runs-on: ubuntu-latest
+    steps:
+      - name: Checkout
+        uses: actions/checkout@v4
+        with:
+          ref: ${{ github.event.pull_request.head.sha || github.sha }}
+
+      - name: Deploy
+        uses: ./.github/actions/deploy
+        with:
+          api-url: ${{ env.TWENTY_DEPLOY_URL }}
+          api-key: ${{ secrets.TWENTY_DEPLOY_API_KEY }}
+
+      - name: Install
+        uses: ./.github/actions/install
+        with:
+          api-url: ${{ env.TWENTY_DEPLOY_URL }}
+          api-key: ${{ secrets.TWENTY_DEPLOY_API_KEY }}

packages/twenty-apps/examples/hello-world/.github/workflows/ci.yml

@@ -25,7 +25,7 @@ jobs:
 
       - name: Spawn Twenty test instance
         id: twenty
-        uses: twentyhq/twenty/.github/actions/spawn-twenty-app-dev-test@feature/sdk-config-file-source-of-truth
+        uses: twentyhq/twenty/.github/actions/spawn-twenty-app-dev-test@main
         with:
           twenty-version: ${{ env.TWENTY_VERSION }}