Feat: support declaring DTOField via Annotated

E.g.:

```py
class A(Struct):
    a: Annotated[int, dto_field("read_only")]
```

For #2351

litestar/contrib/pydantic/pydantic_dto_factory.py

@@ -7,7 +7,7 @@
 
 from litestar.dto.base_dto import AbstractDTO
 from litestar.dto.data_structures import DTOFieldDefinition
-from litestar.dto.field import DTO_FIELD_META_KEY, DTOField
+from litestar.dto.field import DTO_FIELD_META_KEY, extract_dto_field
 from litestar.exceptions import MissingDependencyException, ValidationException
 from litestar.types.empty import Empty
 
@@ -63,7 +63,8 @@ def generate_field_definitions(
 
         for field_name, field_info in model_fields.items():
             field_definition = model_field_definitions[field_name]
-            dto_field = (field_definition.extra or {}).pop(DTO_FIELD_META_KEY, DTOField())
+            dto_field = extract_dto_field(field_definition, field_definition.extra)
+            field_definition.extra.pop(DTO_FIELD_META_KEY, None)
 
             if field_info.default is not PydanticUndefined:
                 default = field_info.default

litestar/dto/dataclass_dto.py

@@ -5,7 +5,7 @@
 
 from litestar.dto.base_dto import AbstractDTO
 from litestar.dto.data_structures import DTOFieldDefinition
-from litestar.dto.field import DTO_FIELD_META_KEY, DTOField
+from litestar.dto.field import extract_dto_field
 from litestar.params import DependencyKwarg, KwargDefinition
 from litestar.types.empty import Empty
 
@@ -40,7 +40,7 @@ def generate_field_definitions(
                 DTOFieldDefinition.from_field_definition(
                     field_definition=field_definition,
                     default_factory=default_factory,
-                    dto_field=dc_field.metadata.get(DTO_FIELD_META_KEY, DTOField()),
+                    dto_field=extract_dto_field(field_definition, dc_field.metadata),
                     model_name=model_type.__name__,
                 ),
                 name=key,

litestar/dto/field.py

@@ -3,13 +3,19 @@
 
 from dataclasses import dataclass
 from enum import Enum
-from typing import Literal
+from typing import TYPE_CHECKING
+
+if TYPE_CHECKING:
+    from typing import Any, Literal, Mapping
+
+    from litestar.typing import FieldDefinition
 
 __all__ = (
     "DTO_FIELD_META_KEY",
     "DTOField",
     "Mark",
     "dto_field",
+    "extract_dto_field",
 )
 
 DTO_FIELD_META_KEY = "__dto__"
@@ -47,3 +53,28 @@ def dto_field(mark: Literal["read-only", "private"] | Mark) -> dict[str, DTOFiel
         Marking a field automates its inclusion/exclusion from DTO field definitions, depending on the DTO's purpose.
     """
     return {DTO_FIELD_META_KEY: DTOField(mark=Mark(mark))}
+
+
+def extract_dto_field(field_definition: FieldDefinition, field_info_mapping: Mapping[str, Any]) -> DTOField:
+    """Extract ``DTOField`` instance for a model field.
+
+    Supports ``DTOField`` to bet set via ``Annotated`` or via a field info/metadata mapping.
+
+    E.g., ``Annotated[str, DTOField(mark="read-only")]`` or ``info=dto_field(mark="read-only")``.
+
+    If a value is found in ``field_info_mapping``, it is prioritized over the field definition's metadata.
+
+    Args:
+        field_definition: A field definition.
+        field_info_mapping: A field metadata/info attribute mapping, e.g., SQLAlchemy's "info" attribute,
+          or dataclasses "metadata" attribute.
+
+    Returns:
+        DTO field info, if any.
+    """
+    if inst := field_info_mapping.get(DTO_FIELD_META_KEY):
+        if not isinstance(inst, DTOField):
+            raise TypeError(f"DTO field info must be an instance of DTOField, got '{inst}'")
+        return inst
+
+    return next((f for f in field_definition.metadata if isinstance(f, DTOField)), DTOField())

litestar/dto/msgspec_dto.py

@@ -7,7 +7,7 @@
 
 from litestar.dto.base_dto import AbstractDTO
 from litestar.dto.data_structures import DTOFieldDefinition
-from litestar.dto.field import DTO_FIELD_META_KEY, DTOField
+from litestar.dto.field import DTO_FIELD_META_KEY, extract_dto_field
 from litestar.types.empty import Empty
 
 if TYPE_CHECKING:
@@ -33,7 +33,8 @@ def default_or_empty(value: Any) -> Any:
 
         for key, field_definition in cls.get_model_type_hints(model_type).items():
             msgspec_field = msgspec_fields[key]
-            dto_field = (field_definition.extra or {}).pop(DTO_FIELD_META_KEY, DTOField())
+            dto_field = extract_dto_field(field_definition, field_definition.extra)
+            field_definition.extra.pop(DTO_FIELD_META_KEY, None)
 
             yield replace(
                 DTOFieldDefinition.from_field_definition(