fix: Add async/await, PDF metadata, and type safety fixes

This commit addresses multiple issues with async operations, PDF metadata
extraction, and type safety in document processing and search.

## Async/Await Fixes
- processor.py:259 - Added await for chunker.chunk_text(content)
- processor.py:270 - Added await for bm25_service.encode_batch(chunk_texts)
- tests/unit/test_document_chunker.py - Converted all 12 test methods to async

## PDF Metadata Enhancement
- pymupdf.py:143 - Added file_size metadata extraction
- pymupdf.py:145-206 - Refactored to extract text page-by-page
  - Manually loop through pages instead of using page_chunks=True
  - Generate page_boundaries metadata for precise page tracking
  - Works around pymupdf.layout.activate() breaking page_chunks=True
- processor.py:32-66 - Added assign_page_numbers() helper function
  - Assigns page numbers to chunks based on overlap with page boundaries
  - Handles chunks spanning multiple pages
- processor.py:298-300 - Call assign_page_numbers() for PDF files

## Type Safety Fixes
- bm25_hybrid.py:184 - Removed int() conversion of doc_id
- semantic.py:131 - Removed int() conversion of doc_id
- viz_routes.py:275 - Removed int() conversion of doc_id
- Added comments documenting that doc_id can be int (notes) or str (file paths)

## Testing
- All 18 tests passing (12 unit + 6 integration)
- No type errors in modified files
- Container logs show successful processing
- Vector viz searches working correctly

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

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

nextcloud_mcp_server/app.py

@@ -122,6 +122,26 @@ def initialize_document_processors():
         except Exception as e:
             logger.warning(f"Failed to register Tesseract processor: {e}")
 
+    # Register PyMuPDF processor (high priority, local, no API required)
+    if "pymupdf" in config["processors"]:
+        pymupdf_config = config["processors"]["pymupdf"]
+        try:
+            from nextcloud_mcp_server.document_processors.pymupdf import (
+                PyMuPDFProcessor,
+            )
+
+            processor = PyMuPDFProcessor(
+                extract_images=pymupdf_config.get("extract_images", True),
+                image_dir=pymupdf_config.get("image_dir"),
+            )
+            registry.register(processor, priority=15)  # Higher than unstructured
+            logger.info(
+                f"Registered PyMuPDF processor: extract_images={pymupdf_config.get('extract_images', True)}"
+            )
+            registered_count += 1
+        except Exception as e:
+            logger.warning(f"Failed to register PyMuPDF processor: {e}")
+
     # Register custom processor
     if "custom" in config["processors"]:
         custom_config = config["processors"]["custom"]