fix: upgrade golangci-lint to v2.1.6 and download tun2socks in CI

.gitea/workflows/main.yml

@@ -46,7 +46,7 @@ jobs:
         uses: golangci/golangci-lint-action@v6
         with:
           install-mode: goinstall
-          version: v1.64.8
+          version: v2.1.6
 
   test-linux:
     name: Test (Linux)
@@ -105,6 +105,9 @@ jobs:
           echo "=== Testing bwrap with user namespace ==="
           bwrap --ro-bind / / --unshare-user --uid 0 --gid 0 -- /bin/echo "bwrap user namespace works!"
 
+      - name: Download tun2socks binaries
+        run: make download-tun2socks
+
       - name: Run unit and integration tests
         run: make test-ci