feat: PWA auction assistant — mobile-first progressive web app

FastAPI backend:
- /api/players — search/filter 505 Serie A players with calibrated prices
- /api/player/name — full detail with ML predictions (quantile P10/P50/P90,
  starter probability, bandit bid recommendation, opponent bid estimate)
- /api/roster — CRUD for live auction roster with budget tracking
- /api/stats — league-wide price distribution
- All ML models loaded on startup (quantile, survival, bandit, opponent, budget)

PWA frontend:
- Installable on iOS/Android via manifest.json + service worker
- Dark theme matching Fantabeto design system
- Player search with role filter, quick-scan list
- Detail sheet with ML intelligence cards
- One-tap bid buttons (market, ML rec, max)
- Live budget bar, roster management
- Works offline for cached assets
- Mobile-first (480px max-width)

Launch: uvicorn pwa.api:app --port 8601
Live at: http://localhost:8601

pwa/static/manifest.json

@@ -0,0 +1,21 @@
+{
+  "name": "Fantabeto Auction",
+  "short_name": "Fantabeto",
+  "description": "Serie A Fantasy Football Auction Assistant",
+  "start_url": "/",
+  "display": "standalone",
+  "background_color": "#0B0F17",
+  "theme_color": "#00D084",
+  "icons": [
+    {
+      "src": "/icons/icon-192.png",
+      "sizes": "192x192",
+      "type": "image/png"
+    },
+    {
+      "src": "/icons/icon-512.png",
+      "sizes": "512x512",
+      "type": "image/png"
+    }
+  ]
+}