docs: Update Contribution Guidelines & architecture documentation with accurate component details

README.md

@@ -26,7 +26,7 @@ yarn start # to start local dev server
 ```bash
 cd backend
 pip install -r requirements.txt # to install all packages
-uvicorn main:app --reload # to run a local server
+uvicorn src.main:app --reload # to run a local server
 ```
 
 If you are getting a `library not found for -lhdf5` error on MacOS, you can try the following

docs/ARCHITECTURE.md

@@ -0,0 +1,169 @@
+# RADIS App Architecture
+
+## System Overview
+
+### High-Level Architecture
+
+```mermaid
+graph TB
+    subgraph "Frontend Layer"
+        UI[React UI]
+        Form[Form Component]
+        Plot[Plot Component]
+        Store[Zustand Store]
+    end
+
+    subgraph "Backend Layer"
+        API[FastAPI Server]
+        Calc[RADIS Calculator]
+        Valid[Pydantic Validator]
+    end
+
+    subgraph "Data Layer"
+        HITRAN[HITRAN Database]
+        Cache[Response Cache]
+    end
+
+    UI --> Form
+    UI --> Plot
+    Form --> Store
+    Plot --> Store
+    Store --> |HTTP POST| API
+    API --> Valid
+    Valid --> Calc
+    Calc --> HITRAN
+    Calc --> Cache
+    Cache --> API
+    API --> |JSON Response| Store
+```
+
+### Request-Response Flow
+
+```mermaid
+sequenceDiagram
+    participant User
+    participant Form
+    participant Store
+    participant API
+    participant Validator
+    participant RADIS
+    participant HITRAN
+
+    User->>Form: Input Parameters
+    Note over Form: Validate Input
+    Form->>Store: Update State
+    Store->>API: POST /calculate-spectrum
+    Note over API: Request Processing
+    API->>Validator: Validate Payload
+    Validator-->>API: Validation Result
+
+    alt Valid Request
+        API->>RADIS: Calculate Spectrum
+        RADIS->>HITRAN: Fetch Molecular Data
+        HITRAN-->>RADIS: Return Data
+        RADIS-->>API: Spectrum Results
+        API-->>Store: JSON Response
+        Store->>Form: Update UI State
+        Form->>User: Show Success
+    else Invalid Request
+        API-->>Store: Error Response
+        Store->>Form: Update Error State
+        Form->>User: Show Error
+    end
+```
+
+### Component Architecture
+
+```mermaid
+classDiagram
+    class Frontend {
+        +components
+        +store
+        +utils
+        +types
+    }
+
+    class Components {
+        +Form
+        +Plot
+        +Fields
+        +ErrorAlert
+    }
+
+    class Store {
+        +formState
+        +plotState
+        +errorState
+        +actions
+    }
+
+    class Backend {
+        +routes
+        +models
+        +services
+        +utils
+    }
+
+    class RADISEngine {
+        +calculate()
+        +fetch_hitran()
+        +process_spectrum()
+    }
+
+    Frontend --> Components
+    Frontend --> Store
+    Components --> Store
+    Backend --> RADISEngine
+    RADISEngine --> HITRAN
+```
+
+### Data Flow Architecture
+
+```mermaid
+flowchart TD
+    subgraph UserInterface
+        A[User Input] --> B[Form Validation]
+        B --> C[State Management]
+        C --> D[API Request]
+    end
+
+    subgraph BackendProcessing
+        D --> E[Request Validation]
+        E --> F[RADIS Calculation]
+        F --> G[Response Formation]
+    end
+
+    subgraph DataVisualization
+        G --> H[Store Update]
+        H --> I[Plot Rendering]
+        I --> J[User Feedback]
+    end
+
+    subgraph ErrorHandling
+        B -- Invalid --> K[Form Error]
+        E -- Invalid --> L[API Error]
+        F -- Failed --> M[Calculation Error]
+    end
+```
+
+## Component Details
+
+### Frontend Components
+- **Form**: Main form component handling user input and validation
+- **Fields**: Sub-components for specific form inputs (molecule, wavelength, etc.)
+- **Plot**: Spectrum visualization component
+- **PlotSpectra**: Component for managing multiple spectra plots
+- **ErrorAlert**: Error display component
+- **Header**: Application header with navigation
+- **InfoPopover**: Information tooltips for form fields
+- **DownloadButtons**: Components for downloading spectrum data
+- **Store**: Zustand store for managing application state
+
+### Backend Components
+- **FastAPI Router**: Handles HTTP requests and routing
+- **Models**: Pydantic models for request/response validation
+- **Helpers**: Utility functions and calculations
+- **Constants**: Application constants and configurations
+- **RADIS Engine**: Integration with RADIS for spectrum calculations
+- **Cache Layer**: Response caching for optimization
+