fix(readme): restore broken star history chart

[FaintFlower]

The star history chart in the README is currently broken and no longer renders, which is unfortunate for a project like DeepChat that wants to showcase its growth.

This change points the chart image and its linking text to a working star history service, restoring the chart in all three README variants (English, Chinese, and Japanese).

No badges or other elements are touched.

Summary by CodeRabbit

• Documentation
  • Updated Star History chart images and links in the English, Japanese, and Chinese README files to use the new star-history.dera.page address.

[coderabbitai]

No actionable comments were generated in the recent review. 🎉

ℹ️ Recent review info

⚙️ Run configuration

Configuration used: defaults

Review profile: CHILL

Plan: Pro Plus

Run ID: b2738784-7187-4260-b152-c81b47e1f32c

📥 Commits

Reviewing files that changed from the base of the PR and between 9fb509b and 28d792e.

📒 Files selected for processing (3)

• README.jp.md
• README.md
• README.zh.md

Included review availability: Your plan provides up to 8 included reviews per hour; 7 remain after this review.

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📝 Walkthrough

Walkthrough

The Star History chart image and destination links now use star-history.dera.page in the Japanese, English, and Chinese README files.

Changes

Star History URL Update

Layer / File(s)	Summary
Update localized Star History links README.jp.md, README.md, README.zh.md	The three README files replace the previous Star History domains with star-history.dera.page.

Estimated code review effort: 1 (Trivial) | ~2 minutes

Merge Risk: ⚪ Minimal · up to 28d79

This is a localized documentation-only change restoring the star history chart across all three README variants. No actionable merge-blocking risk remains after normal link and repository checks.

Suggested reviewers: zerob13, yyhhyyyyyy

🚥 Pre-merge checks | ✅ 5

✅ Passed checks (5 passed)

Check name	Status	Explanation
Description Check	✅ Passed	Check skipped - CodeRabbit’s high-level summary is enabled.
Title check	✅ Passed	The title clearly describes the README fix that restores the broken Star History chart.
Docstring Coverage	✅ Passed	No functions found in the changed files to evaluate docstring coverage. Skipping docstring coverage check.
Linked Issues check	✅ Passed	Check skipped because no linked issues were found for this pull request.
Out of Scope Changes check	✅ Passed	Check skipped because no linked issues were found for this pull request.

✨ Finishing Touches

🧪 Generate unit tests (beta)

• Create PR with unit tests

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