feat: add GitHub Actions workflow for Docker image publishing and update .gitignore for nginx.conf

.github/workflows/docker-publish.yml

@@ -0,0 +1,45 @@
+name: Publish Docker Images
+
+on:
+  push:
+    branches: [main]
+    paths:
+      - 'qwen3-tts-backend/**'
+      - 'qwen3-tts-frontend/**'
+      - 'qwen_tts/**'
+      - 'docker/**'
+
+jobs:
+  build-and-push:
+    runs-on: ubuntu-latest
+    steps:
+      - uses: actions/checkout@v4
+
+      - name: Log in to Docker Hub
+        uses: docker/login-action@v3
+        with:
+          username: ${{ secrets.DOCKERHUB_USERNAME }}
+          password: ${{ secrets.DOCKERHUB_TOKEN }}
+
+      - name: Set up Docker Buildx
+        uses: docker/setup-buildx-action@v3
+
+      - name: Build and push backend
+        uses: docker/build-push-action@v6
+        with:
+          context: .
+          file: docker/backend/Dockerfile
+          push: true
+          tags: bdim404/qwen3-tts-backend:latest
+          cache-from: type=gha,scope=backend
+          cache-to: type=gha,mode=max,scope=backend
+
+      - name: Build and push frontend
+        uses: docker/build-push-action@v6
+        with:
+          context: .
+          file: docker/frontend/Dockerfile
+          push: true
+          tags: bdim404/qwen3-tts-frontend:latest
+          cache-from: type=gha,scope=frontend
+          cache-to: type=gha,mode=max,scope=frontend