feat: Integrate HTML templates with FastAPI

- Created template_helpers.py for centralized template rendering
- Added ux_features.css for enhanced UX styling
- Implemented JavaScript modules for:
  - Keyboard shortcuts (Ctrl+K, Ctrl+R navigation)
  - User preferences persistence
  - Undo/redo functionality (Ctrl+Z/Ctrl+Y)
  - Mobile responsive features
  - Touch gesture support
  - Accessibility features (ARIA, focus management)
  - Screen reader support
  - Color contrast compliance (WCAG)
  - Multi-screen support
- Updated page_controller.py and error_controller.py to use template helpers
- Created comprehensive template integration tests
- All templates verified: index.html, login.html, setup.html, queue.html, error.html
- Maintained responsive layout and theme switching
- Updated instructions.md (removed completed task)
- Updated infrastructure.md with template integration details

src/server/web/static/js/user_preferences.js

@@ -0,0 +1,94 @@
+/**
+ * User Preferences Module
+ * Manages user preferences and settings persistence
+ */
+
+(function() {
+    'use strict';
+
+    const STORAGE_KEY = 'aniworld_preferences';
+
+    /**
+     * Initialize user preferences
+     */
+    function initUserPreferences() {
+        loadPreferences();
+        console.log('[User Preferences] Initialized');
+    }
+
+    /**
+     * Load preferences from localStorage
+     */
+    function loadPreferences() {
+        try {
+            const stored = localStorage.getItem(STORAGE_KEY);
+            if (stored) {
+                const preferences = JSON.parse(stored);
+                applyPreferences(preferences);
+            }
+        } catch (error) {
+            console.error('[User Preferences] Error loading:', error);
+        }
+    }
+
+    /**
+     * Save preferences to localStorage
+     */
+    function savePreferences(preferences) {
+        try {
+            localStorage.setItem(STORAGE_KEY, JSON.stringify(preferences));
+        } catch (error) {
+            console.error('[User Preferences] Error saving:', error);
+        }
+    }
+
+    /**
+     * Apply preferences to the application
+     */
+    function applyPreferences(preferences) {
+        if (preferences.theme) {
+            document.documentElement.setAttribute('data-theme', preferences.theme);
+        }
+        if (preferences.language) {
+            // Language preference would be applied here
+        }
+    }
+
+    /**
+     * Get current preferences
+     */
+    function getPreferences() {
+        try {
+            const stored = localStorage.getItem(STORAGE_KEY);
+            return stored ? JSON.parse(stored) : {};
+        } catch (error) {
+            console.error('[User Preferences] Error getting preferences:', error);
+            return {};
+        }
+    }
+
+    /**
+     * Update specific preference
+     */
+    function updatePreference(key, value) {
+        const preferences = getPreferences();
+        preferences[key] = value;
+        savePreferences(preferences);
+    }
+
+    // Export functions
+    window.UserPreferences = {
+        load: loadPreferences,
+        save: savePreferences,
+        get: getPreferences,
+        update: updatePreference
+    };
+
+    // Initialize on DOM ready
+    if (document.readyState === 'loading') {
+        document.addEventListener('DOMContentLoaded', initUserPreferences);
+    } else {
+        initUserPreferences();
+    }
+
+})();