fix: 窗口边界按 UTC 计算，修复 DST 重复

dataforge/exceptions.py

@@ -0,0 +1,18 @@
+class DataForgeError(Exception):
+    """Base exception."""
+
+
+class ConfigError(DataForgeError):
+    """Invalid dataforge.yml."""
+
+
+class SchemaValidationError(DataForgeError):
+    """Row failed schema validation."""
+
+
+class SourceError(DataForgeError):
+    """Source read failure."""
+
+
+class SinkError(DataForgeError):
+    """Sink write failure."""