[MILESTONE] Documentation and tutorial creation

[FengboMa]

Objective
Create comprehensive documentation and video tutorials for all existing features in Spectraguru. This includes user-facing functionality, developer setup instructions, and usage workflows. The goal is to ensure new users and contributors can easily get started and fully utilize the application.

Implementation
Outline the key steps needed to implement the task:

1. Audit Existing Features:
   Go through the entire app to identify all current features, UI components, and backend functionalities that need documentation.

2. Create Written Documentation:

   • Add or update Markdown-based documentation files for each major section:
     • Installation & Setup
     • Data Upload & Processing
     • Preprocessing Tools
     • Visualization Options
     • Model Training & Prediction (if applicable)
     • Export & Download Features
   • Ensure each doc has code snippets, screenshots, and expected behavior descriptions.

3. Produce Video Tutorials:

   • Record screen walkthroughs with voiceover explaining:
     • Project introduction & core objectives
     • How to install and run locally
     • Step-by-step walkthrough of each major feature
   • Upload to YouTube or embed in the documentation repo (e.g., in the docs/ folder or a GitHub Pages site).

Additional Context

Provide any extra information, screenshots, or links to related documentation that might help in understanding or resolving this task.