Replace old `output` field with new fields across the codebase:
- output_str: Human-readable output summary
- output_json: Structured metadata (optional)
- output_files: Dict of output files with metadata
- output_size: Total size in bytes
- output_mimetypes: CSV of file mimetypes
Files updated:
- api/v1_core.py: Update MinimalArchiveResultSchema to expose new fields
- api/v1_core.py: Update ArchiveResultFilterSchema to search output_str
- cli/archivebox_extract.py: Use output_str in CLI output
- core/admin_archiveresults.py: Update admin fields, search, and fieldsets
- core/admin_archiveresults.py: Fix output_html variable name bug in output_summary
- misc/jsonl.py: Update archiveresult_to_jsonl() to include new fields
- plugins/extractor_utils.py: Update ExtractorResult helper class
The embed_path() method already uses output_files and output_str,
so snapshot detail page and template tags work correctly.
