README Documentation & Professionalism Overhaul

## Description
The current README provides a great baseline, but can be improved to increase developer onboarding speed and project credibility.

## Proposed Improvements
**1. Visual Data Flow (Mermaid.js)**
Add a system architecture diagram to visualize how the MERN stack interacts with Clerk and Cloudinary.

```mermaid
graph TD
Client[React Frontend] <-->|Axios| API[Express API]
API <--> DB[(MongoDB)]
API <--> Auth[Clerk Auth]
API <--> Storage[Cloudinary API]
```

**2. API Documentation Table**
Instead of just listing features, add a clear table of endpoints so contributors know what's available.

| Method | Endpoint | Description | Auth Req. |
| :--- | :--- | :--- | :--- |
| POST | /api/auth/ | User Signup/Login | No |
| GET | /api/hotels | Fetch all listings | No |
| POST | /api/bookings | Create new reservation | Yes |

**3. Expanded Security Implementation**
Document the recently requested security features (Rate limiting, Sanitize, Zod) as a "Security Middleware Stack" section to show the app is production-ready.

**4. Prerequisites & Detailed Setup**
Add a "Prerequisites" section listing specific versions (e.g., Node.js v18+, npm v9+) to avoid "it works on my machine" errors.

**5. Deployment Guide**
Add instructions or badges for Vercel (Frontend) and Render/Railway (Backend) deployment.

**6. Project Screenshots/Gifs**
The placeholder image is a start, but adding a small gallery of the Admin Dashboard and Booking Flow increases user trust.

**Labels:** `documentation`, `DSCWOC'26`, `DSCWOC`

Start with the existing README, package configuration, and API route definitions to verify the listed stack, versions, endpoints, and security features. Done means the README covers the Mermaid architecture, API table, prerequisites, security middleware, deployment targets, and project screenshots or GIFs with accurate project-specific details.

Written by the indexing model from the issue text.