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/client/webdav.py

@@ -1174,7 +1174,9 @@ class WebDAVClient(BaseNextcloudClient):
 
             if display_name_elem is not None and display_name_elem.text == tag_name:
                 tag_info = {
-                    "id": int(tag_id_elem.text) if tag_id_elem is not None else None,
+                    "id": int(tag_id_elem.text)
+                    if tag_id_elem is not None and tag_id_elem.text is not None
+                    else None,
                     "name": display_name_elem.text,
                     "userVisible": user_visible_elem.text.lower() == "true"
                     if user_visible_elem is not None
@@ -1369,7 +1371,9 @@ class WebDAVClient(BaseNextcloudClient):
         )
 
         file_info = {
-            "id": int(fileid_elem.text) if fileid_elem is not None else None,
+            "id": int(fileid_elem.text)
+            if fileid_elem is not None and fileid_elem.text is not None
+            else None,
             "path": path,
             "name": displayname_elem.text
             if displayname_elem is not None