refactor(file_factory): improve filename and mime type determination

[laipz8200]

Checklist:

Important

Please review the checklist below before submitting your pull request.

• Please open an issue before creating a PR or link to an existing issue. Issue with Image Uploads Using “remote_url” on Dify Cloud Solution Post v0.10 Release #9776
• I have performed a self-review of my own code
• I have commented my code, particularly in hard-to-understand areas
• I ran dev/reformat(backend) and cd web && npx lint-staged(frontend) to appease the lint gods

Description

• Simplify filename extraction by always using content disposition if available.
• Default to URL parsing when filename isn't provided in response headers.
• Ensure consistent fallback of 'unknown_file' when filename is missing.
• Clarify mime type handling by using predefined or guessed types more effectively.
• Streamline file size and mime type extraction to handle empty or missing headers gracefully.

Type of Change

• Bug fix (non-breaking change which fixes an issue)
• New feature (non-breaking change which adds functionality)
• Breaking change (fix or feature that would cause existing functionality to not work as expected)
• This change requires a documentation update, included: Dify Document
• Improvement, including but not limited to code refactoring, performance optimization, and UI/UX improvement
• Dependency upgrade

Testing Instructions

Please describe the tests that you ran to verify your changes. Provide instructions so we can reproduce. Please also list any relevant details for your test configuration

• Test A
• Test B