Jul 7 - Implement QR codes for facility

app/models/facility.py

@@ -16,10 +16,21 @@ class Facility(db.Model):
     project_id = db.Column(db.Integer, db.ForeignKey('projects.id', ondelete='SET NULL'),
                            nullable=True, index=True)
 
+    # phase38: unguessable token behind the public QR scan page (/f/<token>).
+    # NULL until first requested — ensure_qr_token() generates it lazily.
+    qr_token = db.Column(db.String(64), unique=True, nullable=True)
+
     # Relationships
     areas = db.relationship('Area', backref='facility', lazy='dynamic')
     inspections = db.relationship('Inspection', backref='facility', lazy='dynamic')
 
+    def ensure_qr_token(self):
+        """Generate the QR token on first use. Caller commits."""
+        if not self.qr_token:
+            import secrets
+            self.qr_token = secrets.token_urlsafe(32)
+        return self.qr_token
+
     def __repr__(self):
         return f'<Facility {self.name}>'