Add likes, follows and playlist visibility; redesign web-player UI

Backend:
- New Likes feature (toggle/get liked tracks) and endpoints
- User follow/unfollow, listening stats, public user profile
- Playlist visibility (public/private) support
- Various auth and DTO/response adjustments to support the above

Frontend (web-player):
- New design system pass: theme tokens/mode (light/dark), glass menu,
  tabs bar, player dock/extras/queue components, mix tiles, artist link
- New routes: Liked, public user profile (/u/[id]), likes API proxy
- Search refactor: shared SearchBox component used by TopBar and
  MobileHeader (search now reachable on mobile), live results as you
  type instead of requiring Enter, dropped the "Buscando…" quick-result
  preview
- Removed now-unused components (MobileNav, CoverBadge, MixBentoTile,
  PlayPauseOverlay, SuggestionsTable, userDirectory)
- Design handoff reference docs added under web-player/design_handoff_musify_player
  and web-player/docs/design-system-refactor-plan.md

Co-Authored-By: Claude Sonnet 5 <noreply@anthropic.com>

web-player/package-lock.json

@@ -10,6 +10,8 @@
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 				"@fontsource-variable/bricolage-grotesque": "^5.3.0",
 				"@fontsource-variable/manrope": "^5.3.0",
+				"@fontsource-variable/plus-jakarta-sans": "^5.3.0",
+				"@fontsource-variable/sora": "^5.3.0",
 				"@lucide/svelte": "^1.23.0",
 				"@sveltejs/adapter-node": "^5.5.7",
 				"jose": "^6.2.3",
@@ -193,6 +195,24 @@
 				"url": "https://github.com/sponsors/ayuhito"
 			}
 		},
+		"node_modules/@fontsource-variable/plus-jakarta-sans": {
+			"version": "5.3.0",
+			"resolved": "https://registry.npmjs.org/@fontsource-variable/plus-jakarta-sans/-/plus-jakarta-sans-5.3.0.tgz",
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+			"license": "OFL-1.1",
+			"funding": {
+				"url": "https://github.com/sponsors/ayuhito"
+			}
+		},
+		"node_modules/@fontsource-variable/sora": {
+			"version": "5.3.0",
+			"resolved": "https://registry.npmjs.org/@fontsource-variable/sora/-/sora-5.3.0.tgz",
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+			"license": "OFL-1.1",
+			"funding": {
+				"url": "https://github.com/sponsors/ayuhito"
+			}
+		},
 		"node_modules/@humanfs/core": {
 			"version": "0.19.2",
 			"resolved": "https://registry.npmjs.org/@humanfs/core/-/core-0.19.2.tgz",