🐛 Make FieldInfoMetadata hashable to fix Annotated type usage in sets

Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>

Author: Yuerchu

sqlmodel/main.py

@@ -199,8 +199,7 @@ def __init__(
         self.sa_relationship_args = sa_relationship_args
         self.sa_relationship_kwargs = sa_relationship_kwargs
 
-
-@dataclass
+@dataclass(unsafe_hash=True)
 class FieldInfoMetadata:
     primary_key: bool | UndefinedType = Undefined
     nullable: bool | UndefinedType = Undefined