redesign, added user system, added api endpoints

core/api.py

@@ -0,0 +1,44 @@
+from ninja import NinjaAPI, Schema
+from typing import List
+from datetime import date
+from decimal import Decimal
+from core.models import Transaction, Category
+
+api = NinjaAPI()
+
+# --- Schemas (Data validation for Flutter) ---
+class CategorySchema(Schema):
+    id: int
+    name: str
+
+class TransactionOut(Schema):
+    id: int
+    title: str
+    amount: Decimal
+    date: date
+    category: CategorySchema | None = None
+
+class TransactionIn(Schema):
+    title: str
+    amount: Decimal
+    date: date
+    category_id: int | None = None
+
+# --- Endpoints ---
+@api.get("/transactions", response=List[TransactionOut])
+def list_transactions(request):
+    return Transaction.objects.select_related('category').all().order_by('-date')
+
+@api.post("/transactions", response=TransactionOut)
+def create_transaction(request, payload: TransactionIn):
+    transaction = Transaction.objects.create(
+        title=payload.title,
+        amount=payload.amount,
+        date=payload.date,
+        category_id=payload.category_id
+    )
+    return transaction
+
+@api.get("/categories", response=List[CategorySchema])
+def list_categories(request):
+    return Category.objects.all()