feat(backend): implemented basic controller layer

7project/backend/app/schemas/category.py

@@ -0,0 +1,23 @@
+from typing import Optional
+from pydantic import BaseModel
+try:
+    # Pydantic v2
+    from pydantic import ConfigDict  # type: ignore
+    _HAS_V2 = True
+except Exception:  # pragma: no cover
+    _HAS_V2 = False
+
+class CategoryBase(BaseModel):
+    name: str
+    description: Optional[str] = None
+
+class CategoryCreate(CategoryBase):
+    pass
+
+class CategoryRead(CategoryBase):
+    id: int
+    if _HAS_V2:
+        model_config = ConfigDict(from_attributes=True)  # type: ignore
+    else:  # Pydantic v1 fallback
+        class Config:  # type: ignore
+            orm_mode = True

7project/backend/app/schemas/transaction.py

@@ -0,0 +1,21 @@
+from typing import List, Optional
+from pydantic import BaseModel, Field
+
+class TransactionBase(BaseModel):
+    amount: float = Field(..., gt=-1e18, lt=1e18)
+    description: Optional[str] = None
+
+class TransactionCreate(TransactionBase):
+    category_ids: Optional[List[int]] = None
+
+class TransactionUpdate(BaseModel):
+    amount: Optional[float] = Field(None, gt=-1e18, lt=1e18)
+    description: Optional[str] = None
+    category_ids: Optional[List[int]] = None
+
+class TransactionRead(TransactionBase):
+    id: int
+    category_ids: List[int] = []
+
+    class Config:
+        from_attributes = True