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.

_edit_models_processing.py

@@ -0,0 +1,45 @@
+from pathlib import Path
+p=Path(r'd:/Projects/Dev/ThreatHunt/backend/app/db/models.py')
+t=p.read_text(encoding='utf-8')
+if 'class ProcessingTask(Base):' in t:
+    print('processing task model already exists')
+    raise SystemExit(0)
+insert='''
+
+# -- Persistent Processing Tasks (Phase 2) ---
+
+class ProcessingTask(Base):
+    __tablename__ = "processing_tasks"
+
+    id: Mapped[str] = mapped_column(String(32), primary_key=True, default=_new_id)
+    hunt_id: Mapped[Optional[str]] = mapped_column(
+        String(32), ForeignKey("hunts.id", ondelete="CASCADE"), nullable=True, index=True
+    )
+    dataset_id: Mapped[Optional[str]] = mapped_column(
+        String(32), ForeignKey("datasets.id", ondelete="CASCADE"), nullable=True, index=True
+    )
+    job_id: Mapped[Optional[str]] = mapped_column(String(64), nullable=True, index=True)
+    stage: Mapped[str] = mapped_column(String(64), nullable=False, index=True)
+    status: Mapped[str] = mapped_column(String(20), default="queued", index=True)
+    progress: Mapped[float] = mapped_column(Float, default=0.0)
+    message: Mapped[Optional[str]] = mapped_column(Text, nullable=True)
+    error: Mapped[Optional[str]] = mapped_column(Text, nullable=True)
+    created_at: Mapped[datetime] = mapped_column(DateTime(timezone=True), default=_utcnow)
+    started_at: Mapped[Optional[datetime]] = mapped_column(DateTime(timezone=True), nullable=True)
+    completed_at: Mapped[Optional[datetime]] = mapped_column(DateTime(timezone=True), nullable=True)
+    updated_at: Mapped[datetime] = mapped_column(
+        DateTime(timezone=True), default=_utcnow, onupdate=_utcnow
+    )
+
+    __table_args__ = (
+        Index("ix_processing_tasks_hunt_stage", "hunt_id", "stage"),
+        Index("ix_processing_tasks_dataset_stage", "dataset_id", "stage"),
+    )
+'''
+# insert before Playbook section
+marker='\n\n# -- Playbook / Investigation Templates (Feature 3) ---\n'
+if marker not in t:
+    raise SystemExit('marker not found for insertion')
+t=t.replace(marker, insert+marker)
+p.write_text(t,encoding='utf-8')
+print('added ProcessingTask model')