Clarify Arize and Phoenix integration positioning

[arizedatngo]

Summary

• Clarifies the Dify integration pages for Arize AX and Arize Phoenix
• Keeps the existing Dify configuration steps intact
• Adds concise context for teams using trace data in evaluation workflows

Why

The Dify docs include separate Arize and Phoenix integration pages. This update makes the AX and Phoenix paths easier to distinguish before setup: AX for full-featured managed cloud or enterprise self-hosted deployments, and Phoenix for open-source local or self-hosted workflows.

Testing

• Docs-only change; not run.

[RiskeyL]

Thanks for the contribution @arizedatngo! We've pushed some edits on top of your branch. Mind taking a look before this merges?

What we changed:

• Polished the wording to match our style guide and unified the cloud/self-host copies (they're parallel trees that stay in sync).
• Added Phoenix Cloud to the Phoenix intros alongside self-hosting. It's the default endpoint in Dify's tracing config, and the only no-infrastructure option for Dify Cloud users.
• Switched relative links to our root-relative convention and dropped the "For more details" callouts, which duplicated links now in the first paragraph.
• Added the zh/ja translations. Every content change in this repo ships all three languages together.

One thing we noticed while reviewing: Dify exports traces from its backend workers, so a Phoenix instance on a developer's machine wouldn't receive traces from Dify Cloud. Only from a self-hosted Dify that can reach it. On that basis we kept the "local development" framing on the self-host pages and pointed Cloud users to Phoenix Cloud or a reachable self-hosted endpoint. Does that match how you see Phoenix used with Dify Cloud? Happy to adjust, and same goes for any of the product descriptions.

[arizedatngo]

@RiskeyL thanks again for pushing edits on top of this branch. Since this is labeled lgtm, could you take one more look when you have a chance and let me know if anything else is needed before merge?

The main intent is to keep the existing Arize/Phoenix setup accurate while clarifying AX vs Phoenix positioning and using the canonical Arize evaluation resource links.