Add player functionality with HLS support and API integration

- Implemented a new Player class in player.js to handle audio playback, including HLS support using hls.js.
- Created a shared API module in api.js for making HTTP requests with proper error handling.
- Added DOM utility functions in dom.js for creating and clearing elements.
- Introduced WebSocket connection handling in ws.js for real-time updates.
- Developed a comprehensive CSS stylesheet for styling the application, including a high-contrast theme.

data/seed/categories.json

@@ -0,0 +1,17 @@
+[
+  { "id": "starter",           "label": "Starter pack",        "icon": "★",  "order": 0 },
+  { "id": "dutch-public",      "label": "Nederlandse publieke","icon": "🇳🇱", "order": 1 },
+  { "id": "dutch-commercial",  "label": "Nederlandse commercieel","icon": "🇳🇱", "order": 2 },
+  { "id": "bbc",               "label": "BBC family",          "icon": "🇬🇧", "order": 3 },
+  { "id": "fip",               "label": "FIP family",          "icon": "🇫🇷", "order": 4 },
+  { "id": "underground",       "label": "Underground & curated","icon": "🌐", "order": 5 },
+  { "id": "ambient",           "label": "Ambient & lo-fi",     "icon": "🌫", "order": 6 },
+  { "id": "electronic",        "label": "Electronic",          "icon": "⚡", "order": 7 },
+  { "id": "jazz",              "label": "Jazz & blues",        "icon": "🎷", "order": 8 },
+  { "id": "classical",         "label": "Classical",           "icon": "🎻", "order": 9 },
+  { "id": "rock",              "label": "Rock & indie",        "icon": "🎸", "order": 10 },
+  { "id": "reggae",            "label": "Reggae & dub",        "icon": "🌴", "order": 11 },
+  { "id": "world",             "label": "World & regional",    "icon": "🌍", "order": 12 },
+  { "id": "soma",              "label": "SomaFM channels",     "icon": "📻", "order": 13 },
+  { "id": "nts",               "label": "NTS infinite mixtapes","icon": "♾", "order": 14 }
+]