add headers to websocket connection

[cbrady]

No description provided.

[bpapillon]

This makes sense and looks good to me. My Claude sweep came up with this, which I have not tested and am not sure whether is valid or not:

- handshake.go — resolveClientVersion(): Because the replicator is the main module (not a dependency), info.Main.Version will be "(devel)" for go build . builds, which is what deployments/Dockerfile runs. The doc
   comment claims "For tagged releases this returns the tag" but that only holds if a consumer runs go install github.com/schematichq/schematic-datastream-replicator@v1.2.3 — not the path CI/CD takes here. In
  practice the X-Schematic-Client-Version header will report (devel) from every Docker build, undermining the ticket's "correlate them to a release" goal.

  - The Dockerfile already passes a real version via -ldflags="-X main.version=${VERSION:-dev} ..." (Dockerfile line ~42), but main.go has no var version string to receive it — a pre-existing dead injection.
  Consider declaring var version string (and commit, buildTime) in main.go and having resolveClientVersion() prefer it when set:
  if version != "" {
      return version
  }