feat: web UI with FastAPI backend, React frontend, and unified launcher

[Ege-BULUT]

Summary

Adds a complete web interface for ScrapeGraphAI: a FastAPI backend with JSONL logging and debug log viewer, a React 19 + Vite + Tailwind frontend, and a unified launcher script to run everything with a single command.

What's included

Launcher (launcher.py)

Single entry point with flags:

• --poe: launch via poe tasks (requires poethepoet)
• --backend-only / --frontend-only: run only one side
• Auto-detects available tools and starts both servers

Backend (webapp/backend/)

FastAPI application with:

• /scrape endpoint accepting prompt, source URL, model selection, and backend choice
• /models endpoint listing available LLM providers and models
• /logs endpoint streaming JSONL-formatted debug logs
• JSONL logging with rotation (configurable via environment)
• Pydantic v2 schemas for request/response validation

Frontend (webapp/frontend/)

React 19 + Vite + Tailwind CSS v3 with:

• ScraperForm with source URL, prompt, model, and backend selectors
• LogViewer for real-time debug log streaming
• ResultViewer with formatted output display
• Tutorial modal with step-by-step guide
• TypeScript throughout

Poe tasks

New poe tasks for development:

• poe web-backend - start the FastAPI dev server
• poe web-frontend - start the Vite dev server
• poe web - run both concurrently

Usage

# Quick start (auto-detects tools)
python launcher.py

# Via poe
poe web

Notes

• Requires Node.js 18+ for the frontend (npm install in webapp/frontend/)
• Docker Compose also available in webapp/docker-compose.yml
• Backend runs on port 8000, frontend dev server on port 5173