feat: Single-port deployment with improved error handling and SvelteKit static build

- Frontend now uses @sveltejs/adapter-static for production builds
- Backend serves both API and static files from single port (originally port 3000)
- Removed all throw statements from services to avoid Elysia prototype errors
- Fixed favicon serving and SvelteKit assets path handling
- Added ecosystem.config.js for PM2 process management
- Comprehensive deployment documentation (PM2 + HAProxy)
- Updated README with single-port architecture
- Created start.sh script for easy production start

src/backend/services/auth.service.js

@@ -30,8 +30,7 @@ async function verifyPassword(password, hash) {
  * @param {string} userData.email - User email
  * @param {string} userData.password - Plain text password
  * @param {string} userData.callsign - Ham radio callsign
- * @returns {Promise<Object>} Created user object (without password)
- * @throws {Error} If email already exists
+ * @returns {Promise<Object|null>} Created user object (without password) or null if email exists
  */
 export async function registerUser({ email, password, callsign }) {
   // Check if user already exists
@@ -42,7 +41,7 @@ export async function registerUser({ email, password, callsign }) {
     .limit(1);
 
   if (existingUser) {
-    throw new Error('Email already registered');
+    return null;
   }
 
   // Hash password
@@ -79,13 +78,13 @@ export async function authenticateUser(email, password) {
     .limit(1);
 
   if (!user) {
-    throw new Error('Invalid email or password');
+    return null;
   }
 
   // Verify password
   const isValid = await verifyPassword(password, user.passwordHash);
   if (!isValid) {
-    throw new Error('Invalid email or password');
+    return null;
   }
 
   // Return user without password hash