fix(chat): fix importing prompts with duplicates & new ones (Issue #1892)

[Gimir]

Description:

• fix import prompts logic to handle duplicates and new propts together

Issues:

• Issue #1892

Checklist:

• [x] the pull request name complies with Conventional Commits
• [x] the pull request name starts with fix(<scope>):, feat(<scope>):, feature(<scope>):, chore(<scope>):, hotfix(<scope>): or e2e(<scope>):. If contains breaking changes then the pull request name must start with fix(<scope>)!:, feat(<scope>)!:, feature(<scope>)!:, chore(<scope>)!:, hotfix(<scope>)!: or e2e(<scope>)!: where <scope> is name of affected project: chat, chat-e2e, overlay, shared, sandbox-overlay, etc.
• [x] the pull request name ends with (Issue #<TICKET_ID>) (comma-separated list of issues)
• [x] I confirm that do not share any confidential information like API keys or any other secrets and private URLs

[Gimir]

/deploy-review

Environment URL: https://chat-ai-dial-chat-pr-1900.nightly-test.deltixhub.io E2E tests status: failed

[Gimir]

/deploy-review

Environment URL: https://chat-ai-dial-chat-pr-1900.nightly-test.deltixhub.io E2E tests status: success