fix AI-131
<!-- This is an auto-generated comment: release notes by coderabbit.ai -->
## Summary by CodeRabbit
- **Refactor**
- Updated database schema to consolidate unique constraints into composite primary keys for embedding-related data, improving consistency.
- Changed the relation in the Snapshot model to allow multiple embeddings.
- Improved filtering logic for documents and snapshots based on embedding existence.
- Reformatted SQL queries and schema attributes for improved readability; no changes to functionality.
<!-- end of auto-generated comment: release notes by coderabbit.ai -->
fix AI-20
<!-- This is an auto-generated comment: release notes by coderabbit.ai -->
## Summary by CodeRabbit
- **New Features**
- Enhanced file metadata with MIME type, blob ID, and file name across context and workspace, now visible in UI and API.
- Added workspace-level matching for files and documents with configurable thresholds and workspace scoping in search queries.
- Introduced a new error type and user-friendly messaging for global workspace context matching failures.
- **Bug Fixes**
- Improved consistent handling of file MIME types and nullable context IDs for accurate metadata.
- **Documentation**
- Updated GraphQL schema, queries, and mutations to include new metadata fields, optional parameters, and error types.
- **Style**
- Added new localization strings for global context matching error messages.
- **Tests**
- Extended test coverage with new and updated snapshot tests for metadata and matching 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
- **Bug Fixes**
- Improved permission checks to ensure users only see document chunks they have read access to.
- Enhanced error handling for clearer and more user-friendly error messages.
<!-- end of auto-generated comment: release notes by coderabbit.ai -->
fix AI-20
fix AI-77
<!-- This is an auto-generated comment: release notes by coderabbit.ai -->
## Summary by CodeRabbit
- **New Features**
- Enhanced relevance-based re-ranking for embedding results, improving the accuracy of content suggestions.
- Added prioritization for workspace content that matches specific document IDs in search results.
- Introduced a new scoped threshold parameter to refine workspace document matching.
- **Improvements**
- Increased default similarity threshold for file chunk matching, resulting in more precise matches.
- Doubled candidate retrieval for file and workspace chunk matching to improve result quality.
- Updated sorting to prioritize context-relevant documents in workspace matches.
- Explicitly included original input content in re-ranking calls for better relevance assessment.
- **Bug Fixes**
- Adjusted re-ranking logic to return only highly relevant results based on confidence scores.
<!-- end of auto-generated comment: release notes by coderabbit.ai -->
