Embed web assets into the Go binary

Serve /static from embedded assets when no static path override is configured, add static route coverage, and update Docker/docs to reflect embedded-by-default behavior.

Co-authored-by: Copilot <223556219+Copilot@users.noreply.github.com>

Dockerfile

@@ -17,9 +17,6 @@ RUN apk add --no-cache ca-certificates docker-cli
 
 WORKDIR /app
 COPY --from=builder /out/webterm /usr/local/bin/webterm
-COPY go/webterm/static /app/static
-
-ENV WEBTERM_STATIC_PATH=/app/static
 
 EXPOSE 8080