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/leaanthony/gosod/gosod.go

@@ -0,0 +1,11 @@
+package gosod
+
+import (
+	"github.com/leaanthony/gosod/internal/templatedir"
+	"io/fs"
+)
+
+// New creates a new TemplateDir structure for the given filesystem
+func New(fs fs.FS) *templatedir.TemplateDir {
+	return templatedir.New(fs)
+}