[feat](proxy,build): enhance HTTP tunneling protocol and add Docker publishing

- Refactored HTTP tunneling protocol to use `protocol.Envelope` for better extensibility.
- Implemented support for message types including HTTP requests, stream handling, and responses.
- Added common security headers like HSTS and X-Forwarded-For processing for improved security and identity handling.
- Introduced GitHub Actions workflow to build and publish Docker images to GHCR.
- Added new protocol structures for stream-based communication in anticipation of future WebSocket/TCP tunneling.
- Updated `go.sum` to remove unused dependencies and reflect new changes.

.github/workflows/docker-publish.yml

@@ -0,0 +1,59 @@
+name: Build and publish HopGate image to GHCR
+
+on:
+  push:
+    branches: [ main ]
+    tags:
+      - 'v*.*.*'
+  workflow_dispatch:
+
+env:
+  IMAGE_NAME: ghcr.io/${{ github.repository_owner }}/hop-gate
+
+jobs:
+  build-and-push:
+    runs-on: ubuntu-latest
+    permissions:
+      contents: read
+      packages: write
+      id-token: write
+
+    steps:
+      - name: Checkout repository
+        uses: actions/checkout@v4
+
+      - name: Set up QEMU
+        uses: docker/setup-qemu-action@v3
+
+      - name: Set up Docker Buildx
+        uses: docker/setup-buildx-action@v3
+
+      - name: Log in to GitHub Container Registry
+        uses: docker/login-action@v3
+        with:
+          registry: ghcr.io
+          username: ${{ github.actor }}
+          password: ${{ secrets.GITHUB_TOKEN }}
+
+      - name: Extract metadata (tags, labels)
+        id: meta
+        uses: docker/metadata-action@v5
+        with:
+          images: ${{ env.IMAGE_NAME }}
+          tags: |
+            type=ref,event=branch
+            type=ref,event=tag
+            type=sha,prefix=sha-,format=short
+            type=raw,value=latest,enable={{is_default_branch}}
+
+      - name: Build and push multi-arch image
+        uses: docker/build-push-action@v5
+        with:
+          context: .
+          file: ./Dockerfile.server
+          push: true
+          platforms: linux/amd64,linux/arm64
+          tags: ${{ steps.meta.outputs.tags }}
+          labels: ${{ steps.meta.outputs.labels }}
+          cache-from: type=gha
+          cache-to: type=gha,mode=max