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.

architecture/08_concepts/03_security.md

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+# Security Concept
+
+CalMiner places a strong emphasis on security to protect sensitive data and ensure the integrity of the system. The following security measures and practices are implemented to safeguard the platform:
+
+## Data Encryption
+
+All sensitive data is encrypted at rest and in transit to prevent unauthorized access.
+
+## Access Controls
+
+Role-based access controls (RBAC) are implemented to restrict data access based on user roles and responsibilities.
+
+Also see [Authentication and Authorization](08_concepts.md#authentication-and-authorization) and the [Data Model](08_02_data_model.md#user-roles) sections.
+
+## Audit Logging
+
+Comprehensive logging of user activities and system events is maintained for monitoring and auditing purposes. Also see [Error Handling and Logging](08_concepts.md#error-handling-and-logging) section for more details.
+
+## Vulnerability Management
+
+Regular security assessments and updates are conducted to identify and mitigate potential vulnerabilities.
+
+## Compliance
+
+The system adheres to relevant regulatory requirements, such as GDPR, to ensure data privacy and protection.
+
+## Architectural Diagram with Security Layers
+
+```mermaid
+architecture-beta
+    group SecurityLayers[Security Layers]
+
+    service FrontendLayer(server)[Frontend Layer] in SecurityLayers
+    service APILayer(server)[API Layer] in SecurityLayers
+    service ServiceLayer(server)[Service Layer] in SecurityLayers
+    service DataAccessLayer(server)[Data Access Layer] in SecurityLayers
+    service DatabaseSystem(database)[Database System] in SecurityLayers
+    service DataStorage(disk)[Encrypted Data Storage] in SecurityLayers
+
+    FrontendLayer:R -- L:APILayer
+    APILayer:R -- L:ServiceLayer
+    ServiceLayer:R -- L:DataAccessLayer
+    DataAccessLayer:R -- L:DatabaseSystem
+    DatabaseSystem:B -- T:DataStorage
+```
+
+```mermaid
+flowchart TD
+    subgraph F[Frontend Layer]
+        Frontend[Frontend Components]
+    end
+    subgraph A[API Layer]
+        APILayer[API Layer]
+    end
+    subgraph S[Service Layer]
+        ServiceLayer[Service Layer]
+    end
+    subgraph D[Data Access Layer]
+        DataAccessLayer[Data Access Layer]
+    end
+    subgraph DB[Database System]
+
+        DatabaseSystem[Database System]
+        DataStorage[Encrypted Data Storage]
+    end
+    Frontend -->|Secure API Calls| APILayer
+    APILayer -->|Authentication & Authorization| ServiceLayer
+    ServiceLayer -->|Data Access| DataAccessLayer
+    DataAccessLayer -->|Database Queries| DatabaseSystem
+    DatabaseSystem -->|Encrypted Data Storage| DataStorage
+
+    classDef securityLayer fill:#f96,stroke:#333,stroke-width:2px;
+    class Frontend,APILayer,ServiceLayer,DataAccessLayer,DatabaseSystem securityLayer;
+```
+
+## Level 2: Security Layers Explanation
+
+### Frontend Layer
+
+The Frontend Layer implements secure communication protocols (e.g., HTTPS) to ensure data transmitted between the client and server is encrypted. It also incorporates input validation to prevent common vulnerabilities such as XSS and CSRF attacks.
+
+### API Layer
+
+The API Layer enforces authentication and authorization mechanisms to control access to backend services. It validates incoming requests and ensures that only authorized users can access specific resources.
+
+### Service Layer
+
+The Service Layer handles business logic while ensuring that data processing adheres to security policies. It also manages session security and implements rate limiting to prevent abuse.
+
+### Data Access Layer
+
+The Data Access Layer is responsible for securely interacting with the database. It uses parameterized queries to prevent SQL injection attacks and ensures that data access is logged for auditing purposes.
+
+### Database System
+
+The Database System employs encryption at rest and in transit to protect sensitive data. It also implements access controls to restrict database access based on user roles.
+Data is regularly backed up, and recovery procedures are in place to ensure data integrity in case of failures.
+
+### Encrypted Data Storage
+
+All sensitive data stored in the system is encrypted using industry-standard encryption algorithms. This ensures that even if data storage is compromised, the data remains protected and inaccessible to unauthorized users.