Add Tier 2 features: Playlist Generator, Artist Deep Dive, Music Timeline

- Playlist Generator: describe a vibe, get a 15-30 song playlist, save or copy as text
- Artist Deep Dive: click any artist name for influences, best album, hidden gems, similar artists
- Music Timeline: visual decade breakdown of your taste with AI insight
- Nav updates: Create Playlist, Timeline links

frontend/src/components/Layout.tsx

@@ -1,6 +1,6 @@
 import { useState } from 'react'
 import { Link, useLocation, useNavigate } from 'react-router-dom'
-import { Disc3, LayoutDashboard, Fingerprint, ListMusic, Compass, Lightbulb, Store, Heart, Crown, Shield, Menu, X, LogOut, User } from 'lucide-react'
+import { Disc3, LayoutDashboard, Fingerprint, Clock, ListMusic, ListPlus, Compass, Lightbulb, Store, Heart, Crown, Shield, Menu, X, LogOut, User } from 'lucide-react'
 import { useAuth } from '../lib/auth'
 
 const ADMIN_EMAIL = 'chris.ryan@deepcutsai.com'
@@ -8,9 +8,11 @@ const ADMIN_EMAIL = 'chris.ryan@deepcutsai.com'
 const baseNavItems = [
   { path: '/dashboard', label: 'Dashboard', icon: LayoutDashboard },
   { path: '/profile', label: 'My Taste', icon: Fingerprint },
+  { path: '/timeline', label: 'Timeline', icon: Clock },
   { path: '/playlists', label: 'Playlists', icon: ListMusic },
   { path: '/discover', label: 'Discover', icon: Compass },
   { path: '/analyze', label: 'Analyze', icon: Lightbulb },
+  { path: '/generate-playlist', label: 'Create Playlist', icon: ListPlus },
   { path: '/bandcamp', label: 'Bandcamp', icon: Store },
   { path: '/saved', label: 'Saved', icon: Heart },
   { path: '/billing', label: 'Pro', icon: Crown },