feat: Add Playbook Manager, Saved Searches, and Timeline View components

- Implemented PlaybookManager for creating and managing investigation playbooks with templates.
- Added SavedSearches component for managing bookmarked queries and recurring scans.
- Introduced TimelineView for visualizing forensic event timelines with zoomable charts.
- Enhanced backend processing with auto-queued jobs for dataset uploads and improved database concurrency.
- Updated frontend components for better user experience and performance optimizations.
- Documented changes in update log for future reference.

_fix_keywords_empty_guard.py

@@ -0,0 +1,25 @@
+from pathlib import Path
+p=Path(r'd:/Projects/Dev/ThreatHunt/backend/app/api/routes/keywords.py')
+t=p.read_text(encoding='utf-8')
+old='''    if not body.dataset_ids and not body.scan_hunts and not body.scan_annotations and not body.scan_messages:
+        raise HTTPException(400, "Select at least one dataset or enable additional sources (hunts/annotations/messages)")
+
+'''
+new='''    if not body.dataset_ids and not body.scan_hunts and not body.scan_annotations and not body.scan_messages:
+        return {
+            "total_hits": 0,
+            "hits": [],
+            "themes_scanned": 0,
+            "keywords_scanned": 0,
+            "rows_scanned": 0,
+            "cache_used": False,
+            "cache_status": "miss",
+            "cached_at": None,
+        }
+
+'''
+if old not in t:
+    raise SystemExit('scope guard block not found')
+t=t.replace(old,new)
+p.write_text(t,encoding='utf-8')
+print('adjusted empty scan guard to return fast empty result (200)')