style: Fix ruff linting issues - quotes and modern type parameters

- Changed single quotes to double quotes (Q000)
- Updated generic functions to use Python 3.12+ type parameters syntax (UP047)
- Removed explicit TypeVar in favor of modern type parameter syntax

🤖 Generated with [Claude Code](https://claude.ai/code)

Co-Authored-By: Claude <[email protected]>

Author: codebydivine

src/thegraph_token_api/models.py

@@ -9,9 +9,6 @@
 
 import inspect
 from dataclasses import dataclass
-from typing import TypeVar
-
-T = TypeVar('T', bound='BaseModel')
 
 
 @dataclass
@@ -309,7 +306,7 @@ class OHLC(BaseModel):
     transactions: float
 
 
-def convert_to_model(data: dict, model_class: type[T]) -> T | None:
+def convert_to_model[T: BaseModel](data: dict, model_class: type[T]) -> T | None:
     """Convert dictionary data to structured model."""
     if not data:
         return None
@@ -359,6 +356,6 @@ def convert_to_model(data: dict, model_class: type[T]) -> T | None:
         return model_class(**working_data)
 
 
-def convert_list_to_models(data_list: list[dict], model_class: type[T]) -> list[T]:
+def convert_list_to_models[T: BaseModel](data_list: list[dict], model_class: type[T]) -> list[T]:
     """Convert list of dictionaries to list of structured models."""
     return [model for item in data_list if item and (model := convert_to_model(item, model_class)) is not None]