feat(ai): implement intelligent auto-tagging system

- Added multi-provider AI infrastructure (OpenAI/Ollama)
- Implemented real-time tag suggestions with debounced analysis
- Created AI diagnostics and database maintenance tools in Settings
- Added automated garbage collection for orphan labels
- Refined UX with deterministic color hashing and interactive ghost tags

keep-notes/components/sidebar.tsx

@@ -4,7 +4,7 @@ import { useState } from 'react'
 import Link from 'next/link'
 import { usePathname, useSearchParams } from 'next/navigation'
 import { cn } from '@/lib/utils'
-import { StickyNote, Bell, Archive, Trash2, Tag, ChevronDown, ChevronUp } from 'lucide-react'
+import { StickyNote, Bell, Archive, Trash2, Tag, ChevronDown, ChevronUp, Settings } from 'lucide-react'
 import { useLabels } from '@/context/LabelContext'
 import { LabelManagementDialog } from './label-management-dialog'
 
@@ -105,6 +105,13 @@ export function Sidebar({ className }: { className?: string }) {
         label="Trash" 
         active={pathname === '/trash'} 
       />
+      <NavItem 
+        href="/settings" 
+        icon={Settings} 
+        label="Settings" 
+        active={pathname === '/settings'} 
+      />
     </aside>
   )
 }
+