/**
 * Sanitization utilities for universal login routes
 *
 * These helpers provide XSS protection and input sanitization for
 * rendering HTML pages with user-controlled or dynamic content.
 */
/**
 * Escape HTML special characters to prevent XSS
 */
export declare function escapeHtml(str: string): string;
/**
 * Escape a string for use in JavaScript string literals
 */
export declare function escapeJs(str: string): string;
/**
 * Escape a URL for safe use inside CSS url("...") function.
 * This prevents CSS injection by escaping characters that could
 * break out of the url() context.
 */
export declare function escapeCssUrl(url: string): string;
/**
 * Sanitize URL for use in href/src attributes
 */
export declare function sanitizeUrl(url: string | undefined): string;
/**
 * Sanitize CSS color value
 */
export declare function sanitizeCssColor(color: string | undefined): string;
/**
 * Build CSS background from page_background (branding format)
 */
export declare function buildPageBackground(pageBackground: string | {
    type?: string;
    start?: string;
    end?: string;
    angle_deg?: number;
} | undefined): string;
/**
 * Build CSS background from theme's page_background (supports background_image_url)
 */
export declare function buildThemePageBackground(themePageBackground: {
    background_color?: string;
    background_image_url?: string;
    page_layout?: string;
} | undefined, fallbackBrandingBackground: string | {
    type?: string;
    start?: string;
    end?: string;
    angle_deg?: number;
} | undefined): string;
/**
 * Safely serialize JSON for embedding in <script> tags
 * Escapes characters that could break out of script context
 */
export declare function safeJsonStringify(obj: unknown): string;
