Closes: [BS-3385](https://linear.app/affine-design/issue/BS-3385/markdown类型的导入，支持media文件和md文件不在同目录的情况)
<!-- This is an auto-generated comment: release notes by coderabbit.ai -->
## Summary by CodeRabbit
- **New Features**
- Added utility functions to resolve and normalize image file paths in markdown and HTML imports.
- Introduced middleware to provide full file path context during file import and transformation.
- Added new types for improved asset and file management in zip imports.
- **Refactor**
- Centralized and simplified image processing logic across HTML, Markdown, and Notion HTML adapters for improved maintainability.
- Enhanced type safety and clarity in file and asset handling during zip imports.
- **Tests**
- Added comprehensive tests for image file path resolution utility.
- **Documentation**
- Improved inline code comments explaining file path resolution logic.
<!-- end of auto-generated comment: release notes by coderabbit.ai -->
<!-- This is an auto-generated comment: release notes by coderabbit.ai -->
## Summary by CodeRabbit
- **New Features**
- Images and icons in bookmark cards are now loaded through an image proxy for improved reliability and consistency.
- Embed blocks for GitHub, Loom, and YouTube now display banner and creator images via an image proxy service for enhanced image loading.
- **Refactor**
- Simplified backend URL handling and proxy logic for images, resulting in more efficient processing and reduced complexity.
- Consolidated image proxy middleware and services into a shared adapter module for streamlined imports and improved maintainability.
<!-- end of auto-generated comment: release notes by coderabbit.ai -->
donteatfriedrice