feat: dSYM 按上传配置一并保存到远端，本地清理后回退到远端地址下载

Co-Authored-By: Claude Sonnet 5 <noreply@anthropic.com>

backend/models.py

@@ -32,6 +32,7 @@ class Task(Base):
     ipa_path = Column(String)
     oss_url = Column(String)
     dsym_path = Column(String)
+    dsym_url = Column(String)
     obfuscation_maps_path = Column(String)
     qr_code_path = Column(String)
     build_dir = Column(String)