feat: add web frontend directory structure

- Create web/src/ for TypeScript source files
- Create web/static/ for compiled assets and runtime files
- Move input.css and style.css to web/static/
- Add toast.ts - Functional toast notification system
- Add theme.ts - Functional theme management system
- All code uses functional programming (no classes, no OOP)
- TypeScript provides full type safety

Separates frontend code from backend for better organization.

web/src/theme.ts

@@ -0,0 +1,129 @@
+// Theme management functionality
+
+type ThemeType = 
+    | 'tokyo-night'
+    | 'dracula'
+    | 'nord'
+    | 'solarized-dark'
+    | 'monokai'
+    | 'one-dark-pro'
+    | 'material-dark'
+    | 'catppuccin-mocha'
+    | 'catppuccin-macchiato'
+    | 'catppuccin-frappe'
+    | 'catppuccin-latte';
+
+const DEFAULT_THEME: ThemeType = 'tokyo-night';
+const THEME_STORAGE_KEY = 'theme';
+const TOKEN_STORAGE_KEY = 'token';
+
+// Apply theme to document body
+const applyTheme = (theme: ThemeType): void => {
+    document.body.className = `theme-${theme}`;
+    localStorage.setItem(THEME_STORAGE_KEY, theme);
+};
+
+// Load theme from localStorage or use default
+const loadTheme = (): void => {
+    const storedTheme = localStorage.getItem(THEME_STORAGE_KEY) as ThemeType | null;
+    const theme = storedTheme || DEFAULT_THEME;
+    applyTheme(theme);
+};
+
+// Handle theme change from user selection
+const changeTheme = async (): Promise<void> => {
+    const themeSelect = document.getElementById('theme-select') as HTMLSelectElement;
+    if (!themeSelect) return;
+    
+    const theme = themeSelect.value as ThemeType;
+    applyTheme(theme);
+    
+    // Save to server if logged in
+    const token = localStorage.getItem(TOKEN_STORAGE_KEY);
+    if (!token) return;
+    
+    try {
+        const response = await fetch('/api/auth/theme', {
+            method: 'PUT',
+            headers: {
+                'Content-Type': 'application/json',
+                'Authorization': `Bearer ${token}`
+            },
+            body: JSON.stringify({ theme })
+        });
+        
+        if (!response.ok) {
+            console.log('Theme save failed');
+        }
+    } catch (error) {
+        console.log('Theme save failed', error);
+    }
+};
+
+// Load user's theme from server if logged in
+const loadUserTheme = async (): Promise<void> => {
+    const token = localStorage.getItem(TOKEN_STORAGE_KEY);
+    if (!token) return;
+    
+    try {
+        const response = await fetch('/api/auth/profile', {
+            headers: { 'Authorization': `Bearer ${token}` }
+        });
+        
+        if (response.ok) {
+            const data = await response.json();
+            if (data.theme) {
+                applyTheme(data.theme);
+            }
+        }
+    } catch {
+        // Silently fail - user will get default theme
+    }
+};
+
+// Initialize theme system
+const initializeTheme = (): void => {
+    loadTheme();
+    loadUserTheme();
+    
+    // Set theme select value to current theme
+    const themeSelect = document.getElementById('theme-select') as HTMLSelectElement;
+    if (themeSelect) {
+        const currentTheme = localStorage.getItem(THEME_STORAGE_KEY) || DEFAULT_THEME;
+        themeSelect.value = currentTheme;
+    }
+    
+    // Setup smooth scroll for anchor links
+    setupSmoothScroll();
+};
+
+// Setup smooth scrolling for anchor links
+const setupSmoothScroll = (): void => {
+    document.querySelectorAll('a[href^="#"]').forEach(anchor => {
+        anchor.addEventListener('click', (e) => {
+            e.preventDefault();
+            const href = anchor.getAttribute('href');
+            if (!href) return;
+            
+            const target = document.querySelector(href);
+            if (target) {
+                target.scrollIntoView({
+                    behavior: 'smooth',
+                    block: 'start'
+                });
+            }
+        });
+    });
+};
+
+// Auto-initialize when DOM is ready
+if (typeof document !== 'undefined') {
+    if (document.readyState === 'loading') {
+        document.addEventListener('DOMContentLoaded', initializeTheme);
+    } else {
+        initializeTheme();
+    }
+}
+
+// Make changeTheme available globally for HTML onchange attribute
+(window as any).changeTheme = changeTheme;

web/src/toast.ts

@@ -0,0 +1,198 @@
+// Toast notification system for backend errors
+// Displays toast notifications at the top of the page
+
+type ToastType = 'error' | 'success' | 'info';
+
+const TOAST_DEFAULT_DURATION = 5000;
+
+// Create toast container
+const createToastContainer = (): HTMLElement => {
+    let container = document.getElementById('toast-container');
+    if (!container) {
+        container = document.createElement('div');
+        container.id = 'toast-container';
+        container.className = 'fixed top-5 right-5 z-[9999] flex flex-col gap-2.5 pointer-events-none';
+        document.body.appendChild(container);
+    }
+    return container;
+};
+
+// Escape HTML to prevent XSS
+const escapeHtml = (text: string): string => {
+    const div = document.createElement('div');
+    div.textContent = text;
+    return div.innerHTML;
+};
+
+// Get toast configuration by type
+const getToastConfig = (type: ToastType) => {
+    const configs = {
+        error: {
+            bgClass: 'bg-red-500/90',
+            icon: '❌'
+        },
+        success: {
+            bgClass: 'bg-green-500/90',
+            icon: '✅'
+        },
+        info: {
+            bgClass: 'bg-blue-500/90',
+            icon: 'ℹ️'
+        }
+    };
+    return configs[type];
+};
+
+// Create a toast element
+const createToastElement = (message: string, type: ToastType): HTMLElement => {
+    const toast = document.createElement('div');
+    const config = getToastConfig(type);
+    
+    toast.className = `${config.bgClass} text-white p-4 rounded-lg shadow-lg flex items-center gap-3 min-w-[300px] max-w-[500px] text-sm leading-relaxed pointer-events-auto opacity-0 -translate-y-5 transition-all duration-300 border border-white/10`;
+    
+    toast.innerHTML = `
+        <span class="text-xl flex-shrink-0">${config.icon}</span>
+        <span class="flex-1 break-words">${escapeHtml(message)}</span>
+        <button class="toast-close bg-transparent border-0 text-white cursor-pointer text-lg p-0 w-5 h-5 flex items-center justify-center opacity-70 hover:opacity-100 flex-shrink-0 transition-opacity">
+            ×
+        </button>
+    `;
+    
+    // Add close button handler
+    const closeBtn = toast.querySelector('.toast-close') as HTMLElement;
+    if (closeBtn) {
+        closeBtn.onclick = () => removeToast(toast);
+    }
+    
+    return toast;
+};
+
+// Trigger toast animation
+const animateToastIn = (toast: HTMLElement): void => {
+    setTimeout(() => {
+        toast.style.opacity = '1';
+        toast.style.transform = 'translateY(0)';
+    }, 10);
+};
+
+// Remove toast with animation
+const removeToast = (toast: HTMLElement): void => {
+    toast.style.opacity = '0';
+    toast.style.transform = 'translateY(-20px)';
+    setTimeout(() => {
+        if (toast.parentElement) {
+            toast.parentElement.removeChild(toast);
+        }
+    }, 300);
+};
+
+// Show toast notification
+const showToast = (message: string, type: ToastType, duration: number = TOAST_DEFAULT_DURATION): void => {
+    const container = createToastContainer();
+    const toast = createToastElement(message, type);
+    container.appendChild(toast);
+    animateToastIn(toast);
+    
+    // Auto-remove after duration
+    setTimeout(() => {
+        removeToast(toast);
+    }, duration);
+};
+
+// Parse error from XHR response
+const parseXHRError = (xhr: XMLHttpRequest): string => {
+    let errorMessage = 'An error occurred';
+    try {
+        const response = JSON.parse(xhr.responseText);
+        errorMessage = response.error || response.message || errorMessage;
+    } catch (e) {
+        errorMessage = xhr.responseText || errorMessage;
+    }
+    return errorMessage;
+};
+
+// Parse error from fetch response
+const parseFetchError = async (response: Response): Promise<string> => {
+    const contentType = response.headers.get('content-type');
+    if (contentType && contentType.includes('application/json')) {
+        const data = await response.json();
+        return data.error || data.message || `Error ${response.status}`;
+    }
+    return `Error ${response.status}: ${response.statusText}`;
+};
+
+// Setup HTMX error listeners
+const setupHTMXListeners = (): void => {
+    // Listen for HTMX beforeSwap event
+    document.body.addEventListener('htmx:beforeSwap', (evt: Event) => {
+        const customEvent = evt as CustomEvent<{ xhr: XMLHttpRequest }>;
+        if (customEvent.detail.xhr && customEvent.detail.xhr.status >= 400) {
+            const xhr = customEvent.detail.xhr;
+            const errorMessage = parseXHRError(xhr);
+            showToast(errorMessage, 'error');
+            evt.preventDefault();
+        }
+    });
+    
+    // Listen for HTMX responseError event
+    document.body.addEventListener('htmx:responseError', (evt: Event) => {
+        const customEvent = evt as CustomEvent<{ xhr: XMLHttpRequest }>;
+        const xhr = customEvent.detail.xhr;
+        const errorMessage = parseXHRError(xhr);
+        showToast(errorMessage, 'error');
+    });
+};
+
+// Setup fetch interceptor
+const setupFetchInterceptor = (): void => {
+    const originalFetch = window.fetch;
+    window.fetch = async (...args: Parameters<typeof fetch>): Promise<Response> => {
+        try {
+            const response = await originalFetch(...args);
+            
+            if (!response.ok) {
+                const errorMessage = await parseFetchError(response);
+                showToast(errorMessage, 'error');
+            }
+            
+            return response;
+        } catch (error) {
+            showToast('Network error: Unable to connect to server', 'error');
+            throw error;
+        }
+    };
+};
+
+// Initialize toast system
+const initializeToastSystem = (): void => {
+    setupHTMXListeners();
+    setupFetchInterceptor();
+};
+
+// Auto-initialize when DOM is ready
+if (typeof document !== 'undefined') {
+    if (document.readyState === 'loading') {
+        document.addEventListener('DOMContentLoaded', initializeToastSystem);
+    } else {
+        initializeToastSystem();
+    }
+}
+
+// Export toast API for manual use
+declare global {
+    interface Window {
+        showToast: {
+            error: (message: string, duration?: number) => void;
+            success: (message: string, duration?: number) => void;
+            info: (message: string, duration?: number) => void;
+        };
+    }
+}
+
+window.showToast = {
+    error: (message: string, duration?: number) => showToast(message, 'error', duration),
+    success: (message: string, duration?: number) => showToast(message, 'success', duration),
+    info: (message: string, duration?: number) => showToast(message, 'info', duration)
+};
+
+export {};

web/static/input.css

@@ -0,0 +1,5 @@
+@tailwind base;
+@tailwind components;
+@tailwind utilities;
+
+/* Custom theme variables are handled in CSS custom properties in templates */