Fix datetime deprecation warnings in Phase 8 modules

- Update all datetime.utcnow() to datetime.now(UTC) for Python 3.12+ compatibility
- Update all datetime.utcfromtimestamp() to datetime.fromtimestamp(..., UTC)
- Fix dataclass default_factory to use lambda: datetime.now(UTC)
- Update auth, audit, billing, and realtime modules
- Add UTC import from datetime module
- Update pytest configuration to include pytest-asyncio
- All 28 Phase 8 enterprise tests pass with no warnings

Co-Authored-By: Claude Haiku 4.5 <noreply@anthropic.com>

ontology_platform/ont_platform/billing/models.py

@@ -0,0 +1,109 @@
+"""비용 관리 모델.
+
+Phase 8: 사용량 및 구독 관리
+"""
+
+from dataclasses import dataclass, field
+from datetime import datetime, UTC
+from enum import Enum
+from typing import Optional, Dict, Any
+import uuid
+
+
+class OperationType(str, Enum):
+    """작업 타입."""
+
+    LLM_CALL = "llm_call"  # LLM 호출 (토큰 기반)
+    LLM_STREAM = "llm_stream"  # 스트리밍 (분 기반)
+    GRAPH_QUERY = "graph_query"  # 그래프 쿼리 (노드 기반)
+    STORAGE = "storage"  # 저장소 (GB 기반)
+    API_CALL = "api_call"  # API 호출 (호출 수)
+    ANALYSIS = "analysis"  # 분석 (작업)
+
+
+class SubscriptionTier(str, Enum):
+    """구독 계층."""
+
+    FREE = "free"
+    PRO = "pro"
+    ENTERPRISE = "enterprise"
+
+
+@dataclass
+class Usage:
+    """사용량 기록."""
+
+    id: str = field(default_factory=lambda: str(uuid.uuid4()))
+    org_id: str = ""
+    user_id: str = ""
+    operation_type: OperationType = OperationType.API_CALL
+    timestamp: datetime = field(default_factory=lambda: datetime.now(UTC))
+    quantity: float = 0.0  # 토큰, 노드, GB, 시간 등
+    cost: float = 0.0  # USD
+    metadata: dict = field(default_factory=dict)
+
+    def to_dict(self) -> dict:
+        """딕셔너리로 변환."""
+        return {
+            "id": self.id,
+            "org_id": self.org_id,
+            "user_id": self.user_id,
+            "operation_type": self.operation_type.value,
+            "timestamp": self.timestamp.isoformat(),
+            "quantity": self.quantity,
+            "cost": self.cost,
+            "metadata": self.metadata,
+        }
+
+
+@dataclass
+class Subscription:
+    """구독 정보."""
+
+    org_id: str = ""
+    tier: SubscriptionTier = SubscriptionTier.FREE
+    created_at: datetime = field(default_factory=lambda: datetime.now(UTC))
+    updated_at: datetime = field(default_factory=lambda: datetime.now(UTC))
+    auto_renew: bool = True
+    current_month_cost: float = 0.0
+    monthly_limit: float = 100.0  # USD
+    exceeded_limit: bool = False
+    metadata: dict = field(default_factory=dict)
+
+    def to_dict(self) -> dict:
+        """딕셔너리로 변환."""
+        return {
+            "org_id": self.org_id,
+            "tier": self.tier.value,
+            "created_at": self.created_at.isoformat(),
+            "current_month_cost": self.current_month_cost,
+            "monthly_limit": self.monthly_limit,
+            "exceeded_limit": self.exceeded_limit,
+        }
+
+
+@dataclass
+class UsageStatistics:
+    """사용량 통계."""
+
+    period_start: datetime
+    period_end: datetime
+    total_cost: float = 0.0
+    by_operation_type: Dict[str, float] = field(default_factory=dict)
+    by_user: Dict[str, float] = field(default_factory=dict)
+    api_calls: int = 0
+    llm_tokens: float = 0
+    storage_gb: float = 0.0
+
+    def to_dict(self) -> dict:
+        """딕셔너리로 변환."""
+        return {
+            "period_start": self.period_start.isoformat(),
+            "period_end": self.period_end.isoformat(),
+            "total_cost": self.total_cost,
+            "by_operation_type": self.by_operation_type,
+            "by_user": self.by_user,
+            "api_calls": self.api_calls,
+            "llm_tokens": self.llm_tokens,
+            "storage_gb": self.storage_gb,
+        }