fix(client): fix editor clipboard copy in non-secure HTTP contexts

[iamraydoan]

Related issue

Closes #2361

Summary

• Fixed SQL Editor Copy and Cut operations failing when Chat2DB Web is deployed over non-HTTPS (HTTP) environments.
• Replaced direct navigator.clipboard.writeText calls in SQLEditorWithOperation/index.tsx with the copyToClipboard utility helper from @/utils/copy.
• The copyToClipboard helper automatically falls back to standard DOM <textarea> selection + document.execCommand('copy') when navigator.clipboard is restricted or throws an error in non-secure contexts.

Affected surfaces

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

Verification

• Commands and results:
  • yarn run lint: PASSED (0 errors, 0 warnings)
  • yarn run test:sql-in-clipboard: PASSED
  • yarn run build:web:community --app_version=0.0.0: PASSED (Compiled successfully in 38.00s)
• Manual verification: Verified copy/cut operations use the fallback mechanism correctly in non-secure HTTP browser contexts.
• UI evidence: N/A

Risk and compatibility

• Public API or stored data: N/A
• Database or driver compatibility: N/A
• Network, privacy, or security: N/A
• Community / Local / Pro boundary: N/A
• Backward compatibility: N/A

Reviewer map

• Start here: chat2db-community-client/src/components/SQLEditor/editor/SQLEditorWithOperation/index.tsx
• Failure condition: N/A
• Rollback or disable path: Revert changes in SQLEditorWithOperation/index.tsx

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: Code refactoring and build verification assisted by Antigravity AI pair programmer.