Fullstack Python LLM Developer

We're looking for Fullstack Python LLM developer to assist us with fixed-price projects and who is also open for part-time opportunities.

Currently we have "hot task that requires estimation, details are below.
Our customer is planning to build a custom internal system and would like to divide the development into three main phases:

Phase 1: Financial System
Phase 2: Communication System
Phase 3: Team Planning & Project Management

Below you will find the detailed scope for Phase 1 (Financial System).

## Phase 1 – Financial System

### Invoicing Module

* Create invoices (with automatic numbering logic)
* PDF generation
* Send invoices via email
* Status tracking (open, paid, overdue)

### Dunning / Reminder System (Important)

* Automated payment reminders
* Multiple dunning levels (e.g. 1–3)
* Custom payment terms per customer

Important:
We need the ability to define customer-specific exceptions, such as:

* Excluding certain customers from automatic reminders
* Individual grace periods
* Manual approval before sending reminders
* Fully manual handling for selected customers
* Notes and history per customer/invoice

### Quotation Module

* Create quotations
* Send via email (optionally printable)
* Status tracking:

* open
* accepted
* declined
* Follow-up function (e.g. automatic “are you still interested?” reminders)

### Order & Recurring Functions

* Order confirmations
* Recurring invoices (for repeat services)

### Product / Service Database

* Manage services and products
* Pricing, units, descriptions
* Reusable across quotations and invoices

### Financial Overview / Controlling

* Track income and expenses
* Categorization (e.g. labor, materials, machines)
* Project-based tracking
* Dashboard overview

### DATEV Integration

* Export for tax advisor
* Structured accounting data (SKR04 preferred)

## Calculation Tool (Core Requirement)

The system must include a calculation tool for project estimation:

* Based on:

* labor (hourly rates)
* machines (we provide cost tables)
* materials (quantity-based, no pricing needed)
* Direct transfer into quotations

## AI-Based Features (Very Important)

### AI Pre-Calculation

* Suggest working hours, team size, machine usage
* Learn from past projects
* Identify risks (e.g. underpricing)

### AI Post-Calculation (Key Feature)

* Compare planned vs. actual results
* Detect deviations (time, cost, efficiency)
* Learn patterns and improve future calculations automatically

### AI-Based Optimization

* Analyze workflows (quotation → project → invoice)
* Identify inefficiencies
* Suggest improvements and automation opportunities

## Technical Requirement

This should be a web-based system with a clean and scalable architecture.

Very important:
The system must be designed in a way that it is fully expandable, since we are planning additional features in later phases, including:

* Communication system (Phase 2)
* Team planning & project management (Phase 3)
Potential future *project visualization tools**

## Additional Notes

This is not a simple tool — we are building a custom internal system (mini-ERP) that should grow with our business.

What we need from you to proceed with this opportunity:

* Your technical approach
* Suggested tech stack
* Timeline estimation
* Experience with similar systems