feat: Reorganize Knowledge taxonomy and enhance collapsed sidebar navigation

[esafwan]

Motivation

The sidebar navigation logic was complex and fragmented, resulting in inconsistent layouts across different application domains (Data, Knowledge, Models, etc.). This PR standardizes the sidebar by adopting a top-level unified navigation structure using Shadcn UI's Sidebar layout.

Changes

1. Unified Sidebar Layout: Reverted the fragmented navigation patterns to a cohesive <UnifiedLayout> component.
2. Accordion Navigation: The primary sidebar now uses a unified accordion logic allowing only one sub-menu to be open at a time for better UX.
3. Collapsed Sidebar Flyouts: When the sidebar is collapsed into a narrow rail, hovering over or clicking a sidebar item displays a clean flyout popover (using DropdownMenu), making navigation fully accessible without awkward rail expansion.
4. Action-Based Taxonomy: The 'Knowledge' sub-items were refactored based on user actions:
   • Tables: For structured/relational data building.
   • Documents: For unstructured document retrieval (RAG).
5. Action Bar Regeneration: Fixed the action buttons (Create/Add) regression within Data and Knowledge pages by properly passing headerActions into the UnifiedLayout.

This resolves the layout jumping, ensures high UX standards, and provides a sleek interaction model reminiscent of modern apps like Linear.