feat(search): add file_path metadata and chunk offsets to search results

Changes:
- Add file_path to metadata in semantic and BM25 hybrid search algorithms
  for PDF viewer integration (search/semantic.py:161-163, search/bm25_hybrid.py:230-232)
- Include chunk_start_offset, chunk_end_offset, page_number, and page_count
  in search results for rich chunk display (api/management.py:981-1004)
- Add point_id field to SearchResult for batch retrieval (models/semantic.py)
- Fix type narrowing for chunk context API parameters (api/management.py:1102-1111)
- Fix None-safety in doc_types discovery (search/algorithms.py:114)

This enables the Astroglobe UI to display PDF pages at the correct
location for matched chunks.

🤖 Generated with [Claude Code](https://claude.com/claude-code)

Co-Authored-By: Claude Sonnet 4.5 <noreply@anthropic.com>

nextcloud_mcp_server/search/semantic.py

@@ -157,6 +157,10 @@ class SemanticSearchAlgorithm(SearchAlgorithm):
                 "total_chunks": result.payload.get("total_chunks"),
             }
 
+            # Add file-specific metadata for PDF viewer
+            if doc_type == "file" and (path := result.payload.get("file_path")):
+                metadata["path"] = path
+
             # Add deck_card-specific metadata for frontend URL construction
             if doc_type == "deck_card":
                 if board_id := result.payload.get("board_id"):
@@ -174,6 +178,7 @@ class SemanticSearchAlgorithm(SearchAlgorithm):
                     chunk_start_offset=result.payload.get("chunk_start_offset"),
                     chunk_end_offset=result.payload.get("chunk_end_offset"),
                     page_number=result.payload.get("page_number"),
+                    page_count=result.payload.get("page_count"),
                     chunk_index=result.payload.get("chunk_index", 0),
                     total_chunks=result.payload.get("total_chunks", 1),
                     point_id=str(result.id),  # Qdrant point ID for batch retrieval