feat: support plugin poll feature

[fatelei]

Description

fix #743

Type of Change

• Bug fix
• New feature
• Refactor
• Performance improvement
• Other

Essential Checklist

Testing

• I have tested the changes locally and confirmed they work as expected
• I have added unit tests where necessary and they pass successfully

Bug Fix (if applicable)

• I have used GitHub syntax to close the related issue (e.g., Fixes #123 or Closes #123)

Additional Information

Please provide any additional context that would help reviewers understand the changes.

[gemini-code-assist]

Code Review

This pull request implements a polling mechanism for model interactions by adding new access actions, API endpoints, and service logic. It introduces ModelPollingResult with custom validation to ensure state consistency and adds corresponding request structures for starting and checking polling status. Reviewer feedback focuses on improving maintainability by replacing magic strings with constants for polling statuses and refining error messages for better debuggability.