Add discovery modes, personalization controls, taste profile page, updated pricing

- Discovery modes: Sonic Twin, Era Bridge, Deep Cuts, Rising Artists
- Discovery dial (Safe to Adventurous slider)
- Block genres/moods exclusion
- Thumbs down/dislike on recommendations
- My Taste page with Genre DNA breakdown, audio feature meters, listening personality
- Updated pricing: Free (5/week), Premium ($6.99/mo), Family ($12.99/mo coming soon)
- Weekly rate limiting instead of daily
- Alembic migration for new fields

frontend/src/components/Layout.tsx

@@ -1,10 +1,11 @@
 import { useState } from 'react'
 import { Link, useLocation, useNavigate } from 'react-router-dom'
-import { Disc3, LayoutDashboard, ListMusic, Compass, Heart, Crown, Menu, X, LogOut, User } from 'lucide-react'
+import { Disc3, LayoutDashboard, Fingerprint, ListMusic, Compass, Heart, Crown, Menu, X, LogOut, User } from 'lucide-react'
 import { useAuth } from '../lib/auth'
 
 const navItems = [
   { path: '/dashboard', label: 'Dashboard', icon: LayoutDashboard },
+  { path: '/profile', label: 'My Taste', icon: Fingerprint },
   { path: '/playlists', label: 'Playlists', icon: ListMusic },
   { path: '/discover', label: 'Discover', icon: Compass },
   { path: '/saved', label: 'Saved', icon: Heart },