feat(PORTFOLIO-002): add position storage costs

app/models/position.py

@@ -22,6 +22,9 @@ class Position:
         entry_date: Date of position entry (for historical conversion lookups)
         entry_basis_mode: Entry basis mode ("weight" or "value_price")
         notes: Optional notes about this position
+        storage_cost_basis: Annual storage cost as percentage (e.g., Decimal("0.12") for 0.12%) or fixed amount
+        storage_cost_period: Period for storage cost ("annual" or "monthly")
+        storage_cost_currency: Currency for fixed amount costs (default "USD")
         created_at: Timestamp when position was created
     """
 
@@ -33,6 +36,9 @@ class Position:
     entry_date: date
     entry_basis_mode: str = "weight"
     notes: str = ""
+    storage_cost_basis: Decimal | None = None
+    storage_cost_period: str | None = None
+    storage_cost_currency: str = "USD"
     created_at: datetime = field(default_factory=lambda: datetime.now(UTC))
 
     def __post_init__(self) -> None:
@@ -67,6 +73,9 @@ class Position:
             "entry_date": self.entry_date.isoformat(),
             "entry_basis_mode": self.entry_basis_mode,
             "notes": self.notes,
+            "storage_cost_basis": str(self.storage_cost_basis) if self.storage_cost_basis is not None else None,
+            "storage_cost_period": self.storage_cost_period,
+            "storage_cost_currency": self.storage_cost_currency,
             "created_at": self.created_at.isoformat(),
         }
 
@@ -82,6 +91,11 @@ class Position:
             entry_date=date.fromisoformat(data["entry_date"]),
             entry_basis_mode=data.get("entry_basis_mode", "weight"),
             notes=data.get("notes", ""),
+            storage_cost_basis=(
+                Decimal(data["storage_cost_basis"]) if data.get("storage_cost_basis") is not None else None
+            ),
+            storage_cost_period=data.get("storage_cost_period"),
+            storage_cost_currency=data.get("storage_cost_currency", "USD"),
             created_at=datetime.fromisoformat(data["created_at"]) if "created_at" in data else datetime.now(UTC),
         )
 
@@ -94,6 +108,9 @@ def create_position(
     entry_date: date | None = None,
     entry_basis_mode: str = "weight",
     notes: str = "",
+    storage_cost_basis: Decimal | None = None,
+    storage_cost_period: str | None = None,
+    storage_cost_currency: str = "USD",
 ) -> Position:
     """Create a new position with sensible defaults.
 
@@ -105,6 +122,9 @@ def create_position(
         entry_date: Entry date (default: today)
         entry_basis_mode: Entry basis mode (default: "weight")
         notes: Optional notes
+        storage_cost_basis: Annual storage cost as percentage or fixed amount (default: None)
+        storage_cost_period: Period for storage cost ("annual" or "monthly", default: None)
+        storage_cost_currency: Currency for fixed amount costs (default: "USD")
     """
     return Position(
         id=uuid4(),
@@ -115,4 +135,7 @@ def create_position(
         entry_date=entry_date or date.today(),
         entry_basis_mode=entry_basis_mode,
         notes=notes,
+        storage_cost_basis=storage_cost_basis,
+        storage_cost_period=storage_cost_period,
+        storage_cost_currency=storage_cost_currency,
     )