Implement complete full-stack authentication system

- Restructure project with separate frontend/backend architecture
- Create dedicated backend with Axum, SQLite, JWT authentication
- Implement real API endpoints for register/login/verify
- Update frontend to use HTTP requests instead of mock auth
- Add bcrypt password hashing and secure token generation
- Separate Cargo.toml files for frontend and backend builds
- Fix Trunk compilation by isolating WASM-incompatible dependencies
- Create demo user in database for easy testing
- Both servers running: frontend (8081), backend (3000)

🤖 Generated with [Claude Code](https://claude.ai/code)

Co-Authored-By: Claude <noreply@anthropic.com>

migrations/001_create_users_table.sql

@@ -0,0 +1,14 @@
+-- Create users table
+CREATE TABLE IF NOT EXISTS users (
+    id TEXT PRIMARY KEY,
+    username TEXT UNIQUE NOT NULL,
+    email TEXT UNIQUE NOT NULL,
+    password_hash TEXT NOT NULL,
+    created_at DATETIME DEFAULT CURRENT_TIMESTAMP,
+    updated_at DATETIME DEFAULT CURRENT_TIMESTAMP
+);
+
+-- Create indexes for performance
+CREATE INDEX IF NOT EXISTS idx_users_username ON users(username);
+CREATE INDEX IF NOT EXISTS idx_users_email ON users(email);
+CREATE INDEX IF NOT EXISTS idx_users_created_at ON users(created_at);