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/schemas/widget.py

@@ -0,0 +1,79 @@
+from pydantic import BaseModel
+from datetime import datetime
+
+
+# === Token schemas ===
+
+class WidgetTokenCreate(BaseModel):
+    """Создание токена виджета"""
+    pass  # Не требует параметров
+
+
+class WidgetTokenResponse(BaseModel):
+    """Ответ с токеном виджета"""
+    id: int
+    token: str
+    created_at: datetime
+    expires_at: datetime | None
+    is_active: bool
+    urls: dict[str, str]  # Готовые URL для виджетов
+
+    class Config:
+        from_attributes = True
+
+
+class WidgetTokenListItem(BaseModel):
+    """Элемент списка токенов"""
+    id: int
+    token: str
+    created_at: datetime
+    is_active: bool
+
+    class Config:
+        from_attributes = True
+
+
+# === Widget data schemas ===
+
+class WidgetLeaderboardEntry(BaseModel):
+    """Запись в лидерборде виджета"""
+    rank: int
+    nickname: str
+    avatar_url: str | None
+    total_points: int
+    current_streak: int
+    is_current_user: bool  # Для подсветки
+
+
+class WidgetLeaderboardResponse(BaseModel):
+    """Ответ лидерборда для виджета"""
+    entries: list[WidgetLeaderboardEntry]
+    current_user_rank: int | None
+    total_participants: int
+    marathon_title: str
+
+
+class WidgetCurrentResponse(BaseModel):
+    """Текущее задание для виджета"""
+    has_assignment: bool
+    game_title: str | None = None
+    game_cover_url: str | None = None
+    assignment_type: str | None = None  # "challenge" | "playthrough"
+    challenge_title: str | None = None
+    challenge_description: str | None = None
+    points: int | None = None
+    difficulty: str | None = None  # easy, medium, hard
+    bonus_completed: int | None = None  # Для прохождений
+    bonus_total: int | None = None
+
+
+class WidgetProgressResponse(BaseModel):
+    """Прогресс участника для виджета"""
+    nickname: str
+    avatar_url: str | None
+    rank: int
+    total_points: int
+    current_streak: int
+    completed_count: int
+    dropped_count: int
+    marathon_title: str