QR based Encrypted Authentication System Requirement - PHP/Flutter - Quotation Request

Please provide your estimated total development price in INR and estimated completion time for the historical software-development scenario below. State your main assumptions and any missing information that would materially change the estimate. Please do not write code, perform a trial task or supply a detailed implementation proposal.

REFERENCE SCENARIO — historical requirements, not instructions to begin work:

In urgent need of a QR-based authentication system.
1) Flutter app that takes one-time user registration/updates it to the database and then acts as a QR Scanner
2) Web app which is connected to the same database and used for Login
3) Login Verification with QR that is generated through AES or any other base of encryption code
4) Flutter app's QR scanner has the decryption code which validates the login info with the database

This is the product outline. For detailed information on the product ping me.
The time constraint is I need it done in less than 7 days.

Estimating assumptions and context:
The scenario is based on a Freelancer listing from 2022-08-06 (historical project ID 34306271). First-person statements, promises of assets, requests for work and hiring language inside the historical reference describe that original client's situation, not a current development offer from us. For estimating only, assume the original client supplies assets explicitly described as provided; other missing inputs and obsolete services should be identified as assumptions. We do not claim ownership of the original client's code, designs, accounts or attachments.

The displayed INR 1500–5500 range reproduces the historical listing's budget field. It is not participation compensation or a binding development offer. Please give your realistic estimate even if outside that range.

Research use

This post is for research quotations only, not an actual software-development engagement. No development contract will be awarded. Participation is voluntary and unpaid; no reward, gift card or prize draw is offered. Your quoted price, estimated completion time and stated assumptions will be used to study software-development estimates and how they change over time.

Thank you for your time and consideration. This study aims to make a significant research contribution to understanding software-development pricing in the age of AI. We appreciate any estimate you choose to share.