Add purchase date picker and sells feature

- Purchase form now includes a date picker (defaults to today)
- New Sell model, CRUD endpoints (/sells), and stats integration
- AddSell and SellList components added to dashboard
- Portfolio chart updated to reflect sells over time

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

btc-portfolio/backend/app/routes/sells.py

@@ -0,0 +1,101 @@
+from fastapi import APIRouter, Depends, HTTPException, status
+from sqlalchemy.orm import Session
+from pydantic import BaseModel, Field
+from typing import List, Optional
+from datetime import datetime
+
+from ..database import get_db
+from .. import models
+from ..dependencies import get_current_user
+
+router = APIRouter()
+
+
+class SellCreate(BaseModel):
+    btc_amount: float = Field(gt=0, le=21_000_000)
+    price_eur: float = Field(gt=0, le=10_000_000)
+    created_at: Optional[datetime] = None
+
+
+class SellUpdate(BaseModel):
+    btc_amount: float = Field(gt=0, le=21_000_000)
+    price_eur: float = Field(gt=0, le=10_000_000)
+    created_at: datetime
+
+
+class SellOut(BaseModel):
+    id: int
+    btc_amount: float
+    price_eur: float
+    created_at: datetime
+
+    class Config:
+        from_attributes = True
+
+
+@router.get("/sells", response_model=List[SellOut])
+def list_sells(
+    db: Session = Depends(get_db),
+    current_user: models.User = Depends(get_current_user),
+):
+    return (
+        db.query(models.Sell)
+        .filter(models.Sell.user_id == current_user.id)
+        .order_by(models.Sell.created_at)
+        .all()
+    )
+
+
+@router.post("/sells", response_model=SellOut, status_code=status.HTTP_201_CREATED)
+def add_sell(
+    sell_in: SellCreate,
+    db: Session = Depends(get_db),
+    current_user: models.User = Depends(get_current_user),
+):
+    sell = models.Sell(
+        btc_amount=sell_in.btc_amount,
+        price_eur=sell_in.price_eur,
+        created_at=sell_in.created_at or datetime.utcnow(),
+        user_id=current_user.id,
+    )
+    db.add(sell)
+    db.commit()
+    db.refresh(sell)
+    return sell
+
+
+@router.put("/sells/{sell_id}", response_model=SellOut)
+def update_sell(
+    sell_id: int,
+    sell_in: SellUpdate,
+    db: Session = Depends(get_db),
+    current_user: models.User = Depends(get_current_user),
+):
+    sell = db.query(models.Sell).filter(
+        models.Sell.id == sell_id,
+        models.Sell.user_id == current_user.id,
+    ).first()
+    if not sell:
+        raise HTTPException(status_code=404, detail="Sell not found")
+    sell.btc_amount = sell_in.btc_amount
+    sell.price_eur = sell_in.price_eur
+    sell.created_at = sell_in.created_at
+    db.commit()
+    db.refresh(sell)
+    return sell
+
+
+@router.delete("/sells/{sell_id}", status_code=status.HTTP_204_NO_CONTENT)
+def delete_sell(
+    sell_id: int,
+    db: Session = Depends(get_db),
+    current_user: models.User = Depends(get_current_user),
+):
+    sell = db.query(models.Sell).filter(
+        models.Sell.id == sell_id,
+        models.Sell.user_id == current_user.id,
+    ).first()
+    if not sell:
+        raise HTTPException(status_code=404, detail="Sell not found")
+    db.delete(sell)
+    db.commit()