Port envd from e2b with internalized shared packages and Connect RPC

- Copy envd source from e2b-dev/infra, internalize shared dependencies
  into envd/internal/shared/ (keys, filesystem, id, smap, utils)
- Switch from gRPC to Connect RPC for all envd services
- Update module paths to git.omukk.dev/wrenn/{sandbox,sandbox/envd}
- Add proto specs (process, filesystem) with buf-based code generation
- Implement full envd: process exec, filesystem ops, port forwarding,
  cgroup management, MMDS integration, and HTTP API
- Update main module dependencies (firecracker SDK, pgx, goose, etc.)
- Remove placeholder .gitkeep files replaced by real implementations

envd/internal/utils/rfsnotify.go

@@ -0,0 +1,12 @@
+package utils
+
+import "path/filepath"
+
+// FsnotifyPath creates an optionally recursive path for fsnotify/fsnotify internal implementation
+func FsnotifyPath(path string, recursive bool) string {
+	if recursive {
+		return filepath.Join(path, "...")
+	}
+
+	return path
+}