Cache Pyodide bundle locally to improve dev server startup time #97

Every uv run pywrangler dev --log-level debug run downloads the same Pyodide bundle from the internet:

..
⎔ Starting local server...
..
Loading Pyodide bundle from internet; url = https://pyodide-capnp-bin.edgeworker.net/pyodide_0.28.2_2025-01-16_9.capnp.bin
[wrangler-ProxyWorker:info] Ready on http://localhost:8787
..

This significantly slows down dev server startup. The bundle could be cached locally and reused across sessions to avoid redundant downloads.

Expected: Pyodide bundle is cached locally and only re-downloaded when the version changes.