better time usings

src/server/models/auth.py

@@ -6,7 +6,7 @@ easy to validate and test.
 """
 from __future__ import annotations
 
-from datetime import datetime
+from datetime import datetime, timezone
 from typing import Optional
 
 from pydantic import BaseModel, Field, constr
@@ -53,5 +53,5 @@ class SessionModel(BaseModel):
 
     session_id: str = Field(..., description="Unique session identifier")
     user: Optional[str] = Field(None, description="Username or identifier")
-    created_at: datetime = Field(default_factory=datetime.utcnow)
+    created_at: datetime = Field(default_factory=lambda: datetime.now(timezone.utc))
     expires_at: Optional[datetime] = Field(None)

src/server/models/download.py

@@ -6,7 +6,7 @@ on serialization, validation, and OpenAPI documentation.
 """
 from __future__ import annotations
 
-from datetime import datetime
+from datetime import datetime, timezone
 from enum import Enum
 from typing import List, Optional
 
@@ -80,8 +80,8 @@ class DownloadItem(BaseModel):
     
     # Timestamps
     added_at: datetime = Field(
-        default_factory=datetime.utcnow,
-        description="When item was added to queue"
+        default_factory=lambda: datetime.now(timezone.utc),
+        description="When item was added to queue",
     )
     started_at: Optional[datetime] = Field(
         None, description="When download started"

src/server/models/websocket.py

@@ -6,7 +6,7 @@ for real-time updates.
 """
 from __future__ import annotations
 
-from datetime import datetime
+from datetime import datetime, timezone
 from enum import Enum
 from typing import Any, Dict, Optional
 
@@ -56,7 +56,7 @@ class WebSocketMessage(BaseModel):
         ..., description="Type of the message"
     )
     timestamp: str = Field(
-        default_factory=lambda: datetime.utcnow().isoformat(),
+        default_factory=lambda: datetime.now(timezone.utc).isoformat(),
         description="ISO 8601 timestamp when message was created",
     )
     data: Dict[str, Any] = Field(
@@ -72,7 +72,7 @@ class DownloadProgressMessage(BaseModel):
         description="Message type",
     )
     timestamp: str = Field(
-        default_factory=lambda: datetime.utcnow().isoformat(),
+        default_factory=lambda: datetime.now(timezone.utc).isoformat(),
         description="ISO 8601 timestamp",
     )
     data: Dict[str, Any] = Field(
@@ -89,7 +89,7 @@ class DownloadCompleteMessage(BaseModel):
         description="Message type",
     )
     timestamp: str = Field(
-        default_factory=lambda: datetime.utcnow().isoformat(),
+        default_factory=lambda: datetime.now(timezone.utc).isoformat(),
         description="ISO 8601 timestamp",
     )
     data: Dict[str, Any] = Field(
@@ -105,7 +105,7 @@ class DownloadFailedMessage(BaseModel):
         description="Message type",
     )
     timestamp: str = Field(
-        default_factory=lambda: datetime.utcnow().isoformat(),
+        default_factory=lambda: datetime.now(timezone.utc).isoformat(),
         description="ISO 8601 timestamp",
     )
     data: Dict[str, Any] = Field(
@@ -121,7 +121,7 @@ class QueueStatusMessage(BaseModel):
         description="Message type",
     )
     timestamp: str = Field(
-        default_factory=lambda: datetime.utcnow().isoformat(),
+        default_factory=lambda: datetime.now(timezone.utc).isoformat(),
         description="ISO 8601 timestamp",
     )
     data: Dict[str, Any] = Field(
@@ -137,7 +137,7 @@ class SystemMessage(BaseModel):
         ..., description="System message type"
     )
     timestamp: str = Field(
-        default_factory=lambda: datetime.utcnow().isoformat(),
+        default_factory=lambda: datetime.now(timezone.utc).isoformat(),
         description="ISO 8601 timestamp",
     )
     data: Dict[str, Any] = Field(
@@ -152,7 +152,7 @@ class ErrorMessage(BaseModel):
         default=WebSocketMessageType.ERROR, description="Message type"
     )
     timestamp: str = Field(
-        default_factory=lambda: datetime.utcnow().isoformat(),
+        default_factory=lambda: datetime.now(timezone.utc).isoformat(),
         description="ISO 8601 timestamp",
     )
     data: Dict[str, Any] = Field(
@@ -167,7 +167,7 @@ class ConnectionMessage(BaseModel):
         ..., description="Connection message type"
     )
     timestamp: str = Field(
-        default_factory=lambda: datetime.utcnow().isoformat(),
+        default_factory=lambda: datetime.now(timezone.utc).isoformat(),
         description="ISO 8601 timestamp",
     )
     data: Dict[str, Any] = Field(
@@ -203,7 +203,7 @@ class ScanProgressMessage(BaseModel):
         description="Message type",
     )
     timestamp: str = Field(
-        default_factory=lambda: datetime.utcnow().isoformat(),
+        default_factory=lambda: datetime.now(timezone.utc).isoformat(),
         description="ISO 8601 timestamp",
     )
     data: Dict[str, Any] = Field(
@@ -220,7 +220,7 @@ class ScanCompleteMessage(BaseModel):
         description="Message type",
     )
     timestamp: str = Field(
-        default_factory=lambda: datetime.utcnow().isoformat(),
+        default_factory=lambda: datetime.now(timezone.utc).isoformat(),
         description="ISO 8601 timestamp",
     )
     data: Dict[str, Any] = Field(
@@ -237,7 +237,7 @@ class ScanFailedMessage(BaseModel):
         description="Message type",
     )
     timestamp: str = Field(
-        default_factory=lambda: datetime.utcnow().isoformat(),
+        default_factory=lambda: datetime.now(timezone.utc).isoformat(),
         description="ISO 8601 timestamp",
     )
     data: Dict[str, Any] = Field(