06/03 Optimize codes, Schwab account

app/models/investment.py

@@ -6,6 +6,9 @@ class Investment(db.Model):
     __tablename__ = 'investments'
 
     id = db.Column(db.Integer, primary_key=True)
+    # Optional link to a PFM account (e.g. Schwab Individual, Schwab Roth IRA).
+    # NULL means the holding is not tied to a specific account.
+    account_id = db.Column(db.Integer, db.ForeignKey('accounts.id'), nullable=True, index=True)
     asset_name = db.Column(db.String(100), nullable=False)
     ticker = db.Column(db.String(20), nullable=True)
     asset_type = db.Column(
@@ -22,6 +25,7 @@ class Investment(db.Model):
     created_at = db.Column(db.DateTime, default=datetime.utcnow)
     updated_at = db.Column(db.DateTime, default=datetime.utcnow, onupdate=datetime.utcnow)
 
+    account = db.relationship('Account', foreign_keys=[account_id])
     inv_transactions = db.relationship('InvestmentTransaction', back_populates='investment',
                                        lazy='dynamic', cascade='all, delete-orphan')