fix(updater): bootstrap fresh venv with deps; rebuild self-update argv from env

- _run_pip: on first venv use, install decnet with its full dep tree so the
  bootstrapped environment actually has typer/fastapi/uvicorn. Subsequent
  updates keep --no-deps for a near-no-op refresh.
- run_update_self: do not reuse sys.argv to re-exec the updater. Inside the
  live process, sys.argv is the uvicorn subprocess invocation (--ssl-keyfile
  etc.), which 'decnet updater' CLI rejects. Reconstruct the operator-visible
  command from env vars set by updater.server.run.

decnet/updater/server.py

@@ -47,6 +47,10 @@ def run(
     os.environ["DECNET_UPDATER_INSTALL_DIR"] = str(install_dir)
     os.environ["DECNET_UPDATER_UPDATER_DIR"] = str(install_dir / "updater")
     os.environ["DECNET_UPDATER_AGENT_DIR"] = str(agent_dir)
+    # Needed by run_update_self to rebuild the updater's launch argv.
+    os.environ["DECNET_UPDATER_BUNDLE_DIR"] = str(updater_dir)
+    os.environ["DECNET_UPDATER_HOST"] = str(host)
+    os.environ["DECNET_UPDATER_PORT"] = str(port)
 
     keyfile = updater_dir / "updater.key"
     certfile = updater_dir / "updater.crt"