Add R2 lifecycle rules by prefix example

[elithrar]

Adds a new example for R2 on how to use Lifecycle Rules to manage content by prefix.

• Shows how to organize a single bucket with prefix-based "directories" for different retention periods (daily, weekly, monthly)
• Includes both Wrangler JSON and S3 API configuration examples
• Demonstrates combining expiration with Infrequent Access storage class transitions
• Covers triggering event notifications per prefix for downstream processing

[github-actions]

This pull request requires reviews from CODEOWNERS as it changes files that match the following patterns:

Pattern	Owners
/src/content/docs/r2/	@oxyjun, @elithrar, @jonesphillip, @aninibread, @harshil1712, @cloudflare/workers-docs, @cloudflare/pcx-technical-writing

[github-actions]

Preview URL: https://3bbfb7a1.preview.developers.cloudflare.com
Preview Branch URL: https://r2-lifecycle-prefix-example.preview.developers.cloudflare.com

Files with changes (up to 15)

Original Link	Updated Link
https://developers.cloudflare.com/r2/examples/temporary-dirs-lifecycle-rules/	https://r2-lifecycle-prefix-example.preview.developers.cloudflare.com/r2/examples/temporary-dirs-lifecycle-rules/