feat: Add detailed metadata to node files listing

Enhance the node files API to include comprehensive file metadata:
- File size in bytes
- File creation time (ISO 8601 format)
- File modification time (ISO 8601 format)
- File extension

Create new NodeFile schema to support these additional fields
while keeping the existing ProjectFile schema for backward compatibility.

This provides users with better information to manage and identify
files in the Web UI.

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

gns3server/schemas/controller/projects.py

@@ -105,6 +105,19 @@ class ProjectFile(BaseModel):
     md5sum: str = Field(..., description="File checksum")
 
 
+class NodeFile(BaseModel):
+    """
+    Detailed file information for node files.
+    """
+
+    path: str = Field(..., description="File name")
+    md5sum: str = Field(..., description="File checksum")
+    size: int = Field(..., description="File size in bytes")
+    created_at: str = Field(..., description="File creation time (ISO 8601)")
+    modified_at: str = Field(..., description="File modification time (ISO 8601)")
+    extension: str = Field(..., description="File extension")
+
+
 class ProjectCompression(str, Enum):
     """
     Supported project compression.