Refactor test files for improved readability and consistency

- Removed unnecessary blank lines and adjusted formatting in test files.
- Ensured consistent use of commas in function calls and assertions across various test cases.
- Updated import statements for better organization and clarity.
- Enhanced mock setups in tests for better isolation and reliability.
- Improved assertions to follow a consistent style for better readability.

app/models/credit_action.py

@@ -118,4 +118,4 @@ def get_all_credit_actions() -> dict[CreditActionType, CreditAction]:
         Dictionary of all credit actions
 
     """
-    return CREDIT_ACTIONS.copy()
+    return CREDIT_ACTIONS.copy()

app/models/credit_transaction.py

@@ -26,4 +26,4 @@ class CreditTransaction(BaseModel, table=True):
     metadata_json: str | None = Field(default=None)
 
     # relationships
-    user: "User" = Relationship(back_populates="credit_transactions")
+    user: "User" = Relationship(back_populates="credit_transactions")

app/models/extraction.py

@@ -1,6 +1,6 @@
 from typing import TYPE_CHECKING
 
-from sqlmodel import Field, Relationship, UniqueConstraint
+from sqlmodel import Field, Relationship
 
 from app.models.base import BaseModel