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/api/envs.go

@@ -0,0 +1,29 @@
+package api
+
+import (
+	"encoding/json"
+	"net/http"
+
+	"git.omukk.dev/wrenn/sandbox/envd/internal/logs"
+)
+
+func (a *API) GetEnvs(w http.ResponseWriter, _ *http.Request) {
+	operationID := logs.AssignOperationID()
+
+	a.logger.Debug().Str(string(logs.OperationIDKey), operationID).Msg("Getting env vars")
+
+	envs := make(EnvVars)
+	a.defaults.EnvVars.Range(func(key, value string) bool {
+		envs[key] = value
+
+		return true
+	})
+
+	w.Header().Set("Cache-Control", "no-store")
+	w.Header().Set("Content-Type", "application/json")
+
+	w.WriteHeader(http.StatusOK)
+	if err := json.NewEncoder(w).Encode(envs); err != nil {
+		a.logger.Error().Err(err).Str(string(logs.OperationIDKey), operationID).Msg("Failed to encode env vars")
+	}
+}