refactor: split schemas.py into schemas/ package

backend/schemas/common.py

@@ -0,0 +1,32 @@
+from pydantic import BaseModel
+from typing import Optional, List
+from datetime import datetime
+
+
+# --- System Settings ---
+class SystemSettingBase(BaseModel):
+    key: str
+    value: str
+
+
+class SystemSetting(SystemSettingBase):
+    class Config:
+        from_attributes = True
+
+
+# --- Database Management ---
+class BackupInfo(BaseModel):
+    filename: str
+    size_bytes: int
+    created_at: datetime
+
+
+class DatabaseStats(BaseModel):
+    backup_count: int
+    total_size_bytes: int
+
+
+class DbSettingsUpdate(BaseModel):
+    retention_count: int
+    schedule_hour: int
+    schedule_freq_days: int