Implement asset upload API and utility functions

- Add Asset and CardLayer model updates
- Create asset upload API endpoints
- Add AssetUploadDialog component
- Create card layout algorithms
- Implement symmetry generation utils
- Add template configurations

backend/apps/projects/models.py

@@ -1,6 +1,7 @@
 from django.db import models
 import uuid
 
+
 class Project(models.Model):
     """项目配置模型"""
     id = models.UUIDField(primary_key=True, default=uuid.uuid4, editable=False)
@@ -24,8 +25,11 @@ class Project(models.Model):
 
 class Asset(models.Model):
     """项目素材模型"""
+    project = models.ForeignKey(Project, on_delete=models.CASCADE, related_name='assets')
     asset_type = models.CharField(max_length=20)  # 'suit_symbol', 'face_card', 'joker', 'back', 'border'
     asset_key = models.CharField(max_length=50)    # 如 'spade', 'heart-J', 'big_joker'
+    file_path = models.CharField(max_length=255)   # 相对于media目录
+    file_name = models.CharField(max_length=100)
     width = models.IntegerField(null=True)
     height = models.IntegerField(null=True)
     uploaded_at = models.DateTimeField(auto_now_add=True)
@@ -33,9 +37,13 @@ class Asset(models.Model):
     def __str__(self):
         return f"{self.asset_type}:{self.asset_key}"
 
+    class Meta:
+        ordering = ['-uploaded_at']
+
 
 class CardLayer(models.Model):
     """牌面图层配置模型"""
+    project = models.ForeignKey(Project, on_delete=models.CASCADE, related_name='layers')
     card_type = models.CharField(max_length=20)  # 'number', 'face', 'joker'
     card_key = models.CharField(max_length=30)   # 'spade-A', 'heart-K', 'big_joker'
     layer_name = models.CharField(max_length=50)
@@ -47,7 +55,6 @@ class CardLayer(models.Model):
 
     # 图层属性（JSON存储）
     properties = models.JSONField(default=dict)
-    file_ref = models.ForeignKey(Asset, on_delete=models.SET_NULL, null=True, related_name='layers')
 
     def __str__(self):
         return f"{self.card_key}-{self.layer_name}"