feat: add FastAPI backend and API documentation

[harshmishra2701]

🚀 Summary

This PR introduces a FastAPI-based REST API alongside the existing Flask UI.

Key additions:

• FastAPI backend for URL shortening
• /api/shorten and /api/version endpoints
• Swagger / OpenAPI documentation
• Dark-themed API landing page
• CLI commands to run UI or API (tiny dev, tiny api)
• Reuse existing short URLs to avoid duplication
• Improved UX messaging in UI
• Added curl-based API verification
• Updated README with API usage, CLI commands, and new features
  Fixes ❇️ [RTY-260001]: add/api on cli #4

🧪 How to Run dev

poetry run tiny dev

open

http://127.0.0.1:8000

🧪 How to Run API

poetry run tiny api

open

http://127.0.0.1:8001

API Test (curl)

▶️ Step 1: Start the FastAPI server

poetry run tiny api

Server will start at:
(http://127.0.0.1:8001)

▶️ Step 2: Create request folder:

In request folder Create a file named input.json in the project root:

{
  "url": "https://recursivezero.com"
}

▶️ Step 3: Send request using curl (Windows PowerShell)

$body = Get-Content .\request\input.json -Raw

Invoke-RestMethod `
  -Uri "http://127.0.0.1:8001/api/shorten" `
  -Method POST `
  -ContentType "application/json" `
  -Body $body

▶️ Step 4: Expected Response

{
  "short_url": "http://127.0.0.1:8001/abc123",
  "original_url": "https://example.com"
}

how to Run lint

poetry run lint

🧩 Related Issue
Issue #4

Test Configuration:

• Browser: Chrome
• Device: Laptop
• Toolchain:
• Python 3.10 / 3.11
• Flask
• FastAPI
• MongoDB
• Poetry

Checklist

• My code follows the style guidelines of this project
• I have performed a self-review of my own code
• I have commented my code, particularly in hard-to-understand areas
• I have made corresponding changes to the documentation
• My changes generate no new warnings
• I have added tests that prove my fix is effective or that my feature works
• Any dependent changes have been merged and published in downstream modules
• I have checked my code and corrected any misspellings

[harshmishra2701]

API running with curl