fix(e2e): create missing .env file and update GitHub Actions syntax

Docker Compose was failing because env_file: .env was referenced but the
file doesn't exist in CI (it's gitignored). Also updates deprecated
set-output command to use GITHUB_OUTPUT environment file.

.github/workflows/e2e-scheduled.yml

@@ -44,7 +44,7 @@ jobs:
       - name: Get npm cache directory
         id: npm-cache-dir
         run: |
-          echo "::set-output name=dir::$(npm config get cache)"
+          echo "dir=$(npm config get cache)" >> $GITHUB_OUTPUT
 
       - uses: actions/cache@v5
         id: npm-cache
@@ -64,6 +64,10 @@ jobs:
 
       - run: npm run env
 
+      - name: Create .env file for Docker Compose
+        run: |
+          cp .env.example .env
+
       - name: Start Docker Services (WebDAV + SuperSync)
         run: |
           docker compose up -d webdav