feat: add secure invitation and reset links

app/models.py

@@ -53,6 +53,20 @@ class PasswordResetToken(db.Model):
     created_by = db.relationship("User", foreign_keys=[created_by_id])
 
 
+class RegistrationInvitation(db.Model):
+    __tablename__ = "registration_invitations"
+
+    id = db.Column(db.Integer, primary_key=True)
+    email = db.Column(db.String(254), nullable=False, index=True)
+    token_hash = db.Column(db.String(64), unique=True, nullable=False, index=True)
+    expires_at = db.Column(db.DateTime, nullable=False, index=True)
+    used_at = db.Column(db.DateTime)
+    created_by_id = db.Column(db.Integer, db.ForeignKey("users.id"), nullable=False)
+    created_at = db.Column(db.DateTime, default=utc_now, nullable=False)
+
+    created_by = db.relationship("User", foreign_keys=[created_by_id])
+
+
 class EmailVerificationCode(db.Model):
     __tablename__ = "email_verification_codes"