Add "More Like This" button and "Why Do I Like This?" analyze feature

- Add Repeat button to RecommendationCard that navigates to Discover
  with a pre-filled query for similar songs
- Read q param on Discover page to pre-fill the query field
- Add POST /api/recommendations/analyze endpoint that uses Claude to
  explain why a user likes a song and suggest similar music
- Create Analyze page with artist/title inputs, analysis card,
  quality tags, and recommendation cards
- Add Analyze nav item and /analyze route

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, Store, Heart, Crown, Shield, Menu, X, LogOut, User } from 'lucide-react'
+import { Disc3, LayoutDashboard, Fingerprint, ListMusic, 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'
@@ -10,6 +10,7 @@ const baseNavItems = [
   { path: '/profile', label: 'My Taste', icon: Fingerprint },
   { path: '/playlists', label: 'Playlists', icon: ListMusic },
   { path: '/discover', label: 'Discover', icon: Compass },
+  { path: '/analyze', label: 'Analyze', icon: Lightbulb },
   { path: '/bandcamp', label: 'Bandcamp', icon: Store },
   { path: '/saved', label: 'Saved', icon: Heart },
   { path: '/billing', label: 'Pro', icon: Crown },