docs: link open-source Chat2DB CLI

[openai0229]

Related issue

N/A - maintainer documentation update for the public Chat2DB CLI repository.

Summary

Links the existing CLI feature entry in all five localized READMEs to the now-public Chat2DB CLI repository and identifies it as open source.

Affected surfaces

• Frontend / Web
• Backend / API / Storage
• Database plugin / Driver
• JCEF / Desktop packaging
• CI / Build / Release
• Documentation only

Verification

• Commands and results: git diff --check passed; rg -n -F https://github.com/OtterMind/Chat2DB-CLI README.md README_CN.md README_ES.md README_JA.md README_KO.md found one linked feature entry in each README.
• Manual verification: Confirmed OtterMind/Chat2DB-CLI is public, active, and publishes release v0.2.1.
• UI evidence: N/A

Risk and compatibility

• Public API or stored data: N/A - documentation only.
• Database or driver compatibility: N/A - documentation only.
• Network, privacy, or security: N/A - links to the official public repository.
• Community / Local / Pro boundary: The linked CLI repository documents support for Community, Pro, and Local.
• Backward compatibility: N/A - no runtime behavior changes.

Reviewer map

• Start here: README.md:22, then the equivalent line in each localized README.
• Failure condition: A localized README omits the public repository link or describes the CLI as closed source.
• Rollback or disable path: Revert commit 581cef9d.

Contributor declaration

• I linked the Issue that defines this change.
• I tested the affected behavior and reported the actual results above.
• I did not include credentials, private data, or generated build output.
• I disclosed substantial AI assistance below, or this PR contains no substantial AI-generated code.

AI assistance: Codex made the five localized documentation edits and verified the resulting diff.