Switch remote deploy to vendored source builds

Move remote deployment to a vendored source bundle built on the target host via Docker so redeploys no longer require local cross-compilation or host Go installation.

Co-Authored-By: Claude Opus 4.7 <noreply@anthropic.com>

vendor/github.com/pkg/browser/browser_windows.go

@@ -0,0 +1,7 @@
+package browser
+
+import "golang.org/x/sys/windows"
+
+func openBrowser(url string) error {
+	return windows.ShellExecute(0, nil, windows.StringToUTF16Ptr(url), nil, nil, windows.SW_SHOWNORMAL)
+}