Add OBS widgets for streamers

- Add widget token authentication system
- Create leaderboard, current assignment, and progress widgets
- Support dark, light, and neon themes
- Add widget settings modal for URL generation
- Fix avatar loading through backend API proxy

🤖 Generated with [Claude Code](https://claude.com/claude-code)

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

backend/app/api/v1/__init__.py

@@ -1,6 +1,6 @@
 from fastapi import APIRouter
 
-from app.api.v1 import auth, users, marathons, games, challenges, wheel, feed, admin, events, assignments, telegram, content, shop, promo
+from app.api.v1 import auth, users, marathons, games, challenges, wheel, feed, admin, events, assignments, telegram, content, shop, promo, widgets
 
 router = APIRouter(prefix="/api/v1")
 
@@ -18,3 +18,4 @@ router.include_router(telegram.router)
 router.include_router(content.router)
 router.include_router(shop.router)
 router.include_router(promo.router)
+router.include_router(widgets.router)