Add Obsidian path input and dedup detection to import UX
- Obsidian source uses path_input: text field for vault folder path
instead of file drop zone, with /api/save-path backend endpoint
- Dedup check on file upload: /api/save returns previous import info
when the same file hash is found in manifests
- Frontend shows inline dedup notice with "Re-import anyway" button
that sets --force flag on the import command
- Handle local filesystem paths in /api/start (skip timestamp rename
logic for paths not under imports/)
Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>