Web Developer for 2D Design App

I am looking for an experienced freelance web developer to build a web application platform for designing heating systems and calculating heat loss through an interactive 2D floor plan editor.

**Project Description:**

The application must allow users to create and edit heating plans for buildings, including automatic heat loss calculations and system sizing.

**Detailed Technical Specifications:**

**1. Frontend - Interactive 2D Editor:**
- Implementation using HTML5 Canvas or SVG for graphic rendering
- Modern JavaScript framework: React, Vue.js, or Angular
- Drag-and-drop functionality for drawing rooms
- Interactive manipulation through visual handles for resizing
- Zoom and pan for plan navigation
- Grid for precise element alignment
- Undo/Redo for operation history
- Export formats: PDF, PNG, DXF, or SVG

**2. Editor Features:**
- Draw rooms with customizable dimensions
- Add windows, doors, radiators, and other elements
- Editable properties for each element (dimensions, material types, insulation)
- Room settings: height, room type, desired temperature
- Multiple selection and editing
- Copy/paste elements
- Library of predefined elements (radiators, standard windows, etc.)

**3. Backend:**
- RESTful API or GraphQL
- Database: PostgreSQL or MongoDB for project storage
- User authentication and authorization (JWT)
- Subscription tiers: free (limited) and Pro (with advanced features)
- Auto-save and project versioning

**4. Thermal Calculations:**
- Calculation engine for heat loss according to standards (EN 12831 or similar)
- Calculations based on:
- Areas and volumes
- Heat transfer coefficients (U-values)
- External and internal temperatures
- Building orientation and climate zones
- Generate reports with calculation results
- Equipment sizing recommendations

**5. User Interface:**
- Responsive design (desktop, tablet)
- Side panel for properties and settings
- Toolbar with drawing tools
- Real-time calculation results display
- Optional dark mode

**6. Additional Requirements:**
- Clean, documented, and modular code
- Optimized performance for complex plans
- Modern browser compatibility (Chrome, Firefox, Safari, Edge)
- User data security
- Automatic project backup

**Expected Deliverables:**
- Complete source code (frontend + backend)
- Detailed technical documentation
- User documentation
- Deployment on cloud platform (AWS, Google Cloud, or Azure)
- Post-launch technical support (period to be negotiated)