fix: resolve all type checking errors (8 errors fixed)

Fixed 8 type checker errors across the codebase:

- vector/scanner.py: Handle None scroll results with null-safe iteration
- search/{bm25_hybrid,semantic}.py: Add None checks for result.payload
- auth/{unified_verifier,webhook_routes}.py: Assert non-None auth credentials
- client/webdav.py: Add None checks before int() conversions
- providers/openai.py: Assert embedding_model is not None
- search/algorithms.py: Explicitly type doc_types set and cast values
- observability/logging_config.py: Match parent class signature (log_data)

Also fixed test_create_tag_creates_system_tag to match WebDAV implementation
(was testing OCS API endpoint, now tests correct WebDAV endpoint with
Content-Location header).

Type checker: 0 errors (down from 8), 20 warnings (ignored)
Tests: All 192 unit tests passing

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

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

nextcloud_mcp_server/observability/logging_config.py

@@ -60,7 +60,7 @@ class TraceContextFormatter(JsonFormatter):
 
     def add_fields(
         self,
-        log_record: dict[str, Any],
+        log_data: dict[str, Any],
         record: logging.LogRecord,
         message_dict: dict[str, Any],
     ) -> None:
@@ -68,28 +68,28 @@ class TraceContextFormatter(JsonFormatter):
         Add custom fields to the log record, including trace context.
 
         Args:
-            log_record: Dictionary to be serialized as JSON
+            log_data: Dictionary to be serialized as JSON
             record: LogRecord instance
             message_dict: Dictionary of extra fields from log call
         """
         # Call parent to add standard fields
-        super().add_fields(log_record, record, message_dict)
+        super().add_fields(log_data, record, message_dict)
 
         # Add trace context if available
         trace_context = get_trace_context()
         if trace_context:
-            log_record["trace_id"] = trace_context.get("trace_id")
-            log_record["span_id"] = trace_context.get("span_id")
+            log_data["trace_id"] = trace_context.get("trace_id")
+            log_data["span_id"] = trace_context.get("span_id")
 
         # Add standard fields with consistent naming
-        log_record["timestamp"] = self.formatTime(record)
-        log_record["level"] = record.levelname
-        log_record["logger"] = record.name
-        log_record["message"] = record.getMessage()
+        log_data["timestamp"] = self.formatTime(record)
+        log_data["level"] = record.levelname
+        log_data["logger"] = record.name
+        log_data["message"] = record.getMessage()
 
         # Include exception info if present
         if record.exc_info:
-            log_record["exception"] = self.formatException(record.exc_info)
+            log_data["exception"] = self.formatException(record.exc_info)
 
 
 class TraceContextTextFormatter(logging.Formatter):