fix(cloudflare): route asset upload sessions to the dispatch-namespace endpoint

[pltoledo]

Asset upload sessions for Workers deployed into a dispatch namespace were created on the account-level endpoint, so the completion JWT comes back scoped to the wrong script identity and the namespaced script PUT is rejected (400 on a new script, 500 on an existing one).

uploadAssets now takes the namespace and picks the endpoint the same way the namespace-aware helpers in WorkerProvider already do (putWorkerScript, getScriptSettings, deleteWorkerScript):

const session = dispatchNamespace
  ? yield* wfp.createDispatchNamespaceScriptAssetUpload({
      accountId,
      dispatchNamespace,
      scriptName: workerName,
      manifest: assets.manifest,
    })
  : yield* workers.createScriptAssetUpload({
      accountId,
      scriptName: workerName,
      manifest: assets.manifest,
    });

The version-upload call site is unchanged: namespaced scripts have no versions API and the provider already rejects version + namespace.

We run this change in production as a patch over 2.0.0-beta.72 (Workers for Platforms platform publishing sites into a dispatch namespace, static assets + prebuilt SSR workers); with it, Worker with namespace and assets deploys end to end.

[sam-goodwin]

Please add a regression test