Japanese README is missing recent observability and setup-help updates

### Self Checks

- [x] I have read the [Contributing Guide](https://github.com/langgenius/dify/blob/main/CONTRIBUTING.md) and [Language Policy](https://github.com/langgenius/dify/issues/1542).
- [x] I have searched for existing issues and pull requests, including closed ones.
- [x] I confirm that I am using English to submit this report.

### Problem

The Japanese README has drifted behind the root English README in two small, user-facing places:

1. The introductory observability text does not include the current Opik, Langfuse, and Arize Phoenix integration links.
2. The Quick Start section goes directly from installation to the source-deployment note and omits the newer FAQ / community help guidance.

The Simplified Chinese README was recently synchronized for the same class of drift in #42161. I could not find an existing issue or PR covering the Japanese README.

### Expected Behavior

`docs/ja-JP/README.md` should retain the Japanese translation while reflecting the current root README's observability integrations and setup-help links.

### Proposed scope

- Add the three current observability integration links to the Japanese introduction.
- Add a short Japanese “Seeking help” subsection after Quick Start that links to the self-hosting FAQ and the existing Japanese Community & Contact section.
- No other translation or structural changes.

I can submit this narrow synchronization immediately.

Compare docs/ja-JP/README.md with the root English README, focusing on the introductory observability links and the Quick Start section. Preserve the Japanese translation, add the Opik, Langfuse, Arize Phoenix links and the Japanese help subsection, and consider the work done when those two areas match the current English guidance without other structural changes.

Written by the indexing model from the issue text.