Add project documentation and architecture details

- Create .gitignore to exclude specific project files and directories.
- Add CONTRIBUTING.md with guidelines for contributing to the project.
- Update README.md to reflect changes in usage section and contact information.
- Introduce 08_concepts.md outlining cross-cutting concepts in the architecture.
- Add 02_data_model.md detailing the data model and relationships.
- Implement 03_security.md to describe security measures and practices.
- Establish 08_ui_design.md for user interface design principles.
- Document quality requirements in 10_quality_requirements.md.
- Identify risks and technical debts in 11_technical_risks.md.
- Create a glossary in 12_glossary.md for project-specific terms.
- Include about-arc42.md to explain the arc42 documentation template.
- Define price calculation variables and formula in price_calculation.md.
- Introduce ADR template in adr.md for documenting architecture decisions.

CONTRIBUTING.md

@@ -0,0 +1,15 @@
+# Contributing to Calminer
+
+We welcome contributions to Calminer! If you would like to contribute, please follow these guidelines:
+
+1. **Fork the Repository**: Create a personal copy of the repository on your GitHub account.
+
+2. **Create a Branch**: Before making changes, create a new branch for your feature or bug fix.
+
+3. **Make Your Changes**: Implement your changes in the new branch.
+
+4. **Write Tests**: Ensure that your changes are covered by tests.
+
+5. **Submit a Pull Request**: Once you are satisfied with your changes, submit a pull request to the main repository.
+
+Thank you for your interest in contributing to Calminer!