Update the Cloudflare-related hosting guides

[niusia-ua]

Since March 17 2025, workers can access environment variables and secrets from the global scope.
https://developers.cloudflare.com/changelog/2025-03-17-importable-env

Now, we can set up bots outside the fetch method, which is a much better approach than before.

[ztm0929]

Perhaps we could also update the configuration-related demo. As it stands, Cloudflare now seems to default to using wrangler.jsonc instead of wrangler.toml.

FYI:
https://developers.cloudflare.com/workers/wrangler/configuration/

[KnorpelSenf]

That sounds reasonable. @ztm0929 do you feel like contributing these changes so we can close this issue?