05/31 Phase 1: initial codes

app/models/fx_rate.py

@@ -0,0 +1,15 @@
+from app.extensions import db
+from datetime import datetime
+
+
+class FxRate(db.Model):
+    __tablename__ = 'fx_rates'
+
+    id = db.Column(db.Integer, primary_key=True)
+    date = db.Column(db.Date, nullable=False, unique=True, index=True)
+    usd_to_vnd = db.Column(db.Numeric(12, 2), nullable=False)
+    source = db.Column(db.String(50), nullable=True)  # 'exchangerate-api' | 'vcb' | 'manual'
+    fetched_at = db.Column(db.DateTime, default=datetime.utcnow)
+
+    def __repr__(self):
+        return f'<FxRate {self.date} 1USD={self.usd_to_vnd}VND>'