chore(docker): optimize Dockerfiles and add healthchecks for Coolify deployment

- Add build arguments and environment variables for OAuth client IDs in frontend Dockerfile
- Install wget and add HEALTHCHECK commands to frontend and backend Dockerfiles
- Create non-root user in backend Dockerfile for improved security
- Update docker-compose.yml with healthcheck configurations and dynamic port/environment variable support
- Add network configuration and restart policies to docker-compose services
- Expand .env.example with additional OAuth secrets, ports, and environment variables for Coolify
- Enhance README.md with detailed Coolify deployment instructions and required environment variables table

.env.example

@@ -1,10 +1,38 @@
+# CloudStream Transfer - Environment Variables
+# Copy this file to .env and fill in your values
+
+# ======================
+# OAuth Credentials
+# ======================
+
 # Microsoft Azure AD OAuth Configuration
 # Get your client ID from: https://portal.azure.com -> Azure Active Directory -> App registrations
 VITE_MS_CLIENT_ID=your_microsoft_client_id_here
+MS_CLIENT_SECRET=your_microsoft_client_secret_here
 
-# Google Cloud OAuth Configuration
+# Google Cloud OAuth Configuration  
 # Get your client ID from: https://console.cloud.google.com -> APIs & Services -> Credentials
 VITE_GOOGLE_CLIENT_ID=your_google_client_id_here
+GOOGLE_CLIENT_SECRET=your_google_client_secret_here
 
-# Note: Redirect URI should be set to your domain + /auth/callback
+# ======================
+# URLs & Redirects
+# ======================
+
+# For Coolify: Use your domain (e.g., https://cloudstream.yourdomain.com/auth/callback)
 # For local development: http://localhost:5173/auth/callback
+REDIRECT_URI=http://localhost:5173/auth/callback
+
+# Optional: Override API URL if backend is on different domain
+# VITE_API_URL=https://api.yourdomain.com
+
+# ======================
+# Ports (Coolify will override these)
+# ======================
+FRONTEND_PORT=80
+BACKEND_PORT=3001
+
+# ======================
+# Environment
+# ======================
+NODE_ENV=production