feat(fonts): implement Phase 1 - Create Proxy API Client

- Created src/entities/Font/api/proxy/proxyFonts.ts
- Implemented fetchProxyFonts function with full pagination support
- Implemented fetchProxyFontById convenience function
- Added TypeScript interfaces: ProxyFontsParams, ProxyFontsResponse
- Added comprehensive JSDoc documentation
- Updated src/entities/Font/api/index.ts to export proxy API

Phase 1/7: Proxy API Integration for GlyphDiff

src/entities/Font/api/index.ts

@@ -4,6 +4,17 @@
  * Exports API clients and normalization utilities
  */
 
+// Proxy API (PRIMARY - NEW)
+export {
+    fetchProxyFontById,
+    fetchProxyFonts,
+} from './proxy/proxyFonts';
+export type {
+    ProxyFontsParams,
+    ProxyFontsResponse,
+} from './proxy/proxyFonts';
+
+// Google Fonts API (DEPRECATED - kept for backward compatibility)
 export {
     fetchGoogleFontFamily,
     fetchGoogleFonts,
@@ -14,6 +25,7 @@ export type {
     GoogleFontsResponse,
 } from './google/googleFonts';
 
+// Fontshare API (DEPRECATED - kept for backward compatibility)
 export {
     fetchAllFontshareFonts,
     fetchFontshareFontBySlug,

src/entities/Font/api/proxy/proxyFonts.ts

@@ -0,0 +1,160 @@
+/**
+ * Proxy API client
+ *
+ * Handles API requests to GlyphDiff proxy API for fetching font metadata.
+ * Provides error handling, pagination support, and type-safe responses.
+ *
+ * Proxy API normalizes font data from Google Fonts and Fontshare into a single
+ * unified format, eliminating the need for client-side normalization.
+ *
+ * @see https://api.glyphdiff.com/api/v1/fonts
+ */
+
+import { api } from '$shared/api/api';
+import { buildQueryString } from '$shared/lib/utils';
+import type { QueryParams } from '$shared/lib/utils';
+import type { UnifiedFont } from '../../model/types';
+import type {
+    FontCategory,
+    FontSubset,
+} from '../../model/types';
+
+/**
+ * Proxy API base URL
+ */
+const PROXY_API_URL = 'https://api.glyphdiff.com/api/v1/fonts' as const;
+
+/**
+ * Proxy API parameters
+ *
+ * Maps directly to the proxy API query parameters
+ */
+export interface ProxyFontsParams extends QueryParams {
+    /**
+     * Font provider filter ("google" or "fontshare")
+     * Omit to fetch from both providers
+     */
+    provider?: 'google' | 'fontshare';
+
+    /**
+     * Font category filter
+     */
+    category?: FontCategory;
+
+    /**
+     * Character subset filter
+     */
+    subset?: FontSubset;
+
+    /**
+     * Search query (e.g., "roboto", "satoshi")
+     */
+    q?: string;
+
+    /**
+     * Sort order for results
+     * "name" - Alphabetical by font name
+     * "popularity" - Most popular first
+     * "lastModified" - Recently updated first
+     */
+    sort?: 'name' | 'popularity' | 'lastModified';
+
+    /**
+     * Number of items to return (pagination)
+     */
+    limit?: number;
+
+    /**
+     * Number of items to skip (pagination)
+     * Use for pagination: offset = (page - 1) * limit
+     */
+    offset?: number;
+}
+
+/**
+ * Proxy API response
+ *
+ * Includes pagination metadata alongside font data
+ */
+export interface ProxyFontsResponse {
+    /** Array of unified font objects */
+    fonts: UnifiedFont[];
+
+    /** Total number of fonts matching the query */
+    total: number;
+
+    /** Limit used for this request */
+    limit: number;
+
+    /** Offset used for this request */
+    offset: number;
+}
+
+/**
+ * Fetch fonts from proxy API
+ *
+ * @param params - Query parameters for filtering and pagination
+ * @returns Promise resolving to proxy API response
+ * @throws ApiError when request fails
+ *
+ * @example
+ * ```ts
+ * // Fetch all sans-serif fonts from Google
+ * const response = await fetchProxyFonts({
+ *     provider: 'google',
+ *     category: 'sans-serif',
+ *     limit: 50,
+ *     offset: 0
+ * });
+ *
+ * // Search fonts across all providers
+ * const searchResponse = await fetchProxyFonts({
+ *     q: 'roboto',
+ *     limit: 20
+ * });
+ *
+ * // Fetch fonts with pagination
+ * const page1 = await fetchProxyFonts({ limit: 50, offset: 0 });
+ * const page2 = await fetchProxyFonts({ limit: 50, offset: 50 });
+ * ```
+ */
+export async function fetchProxyFonts(
+    params: ProxyFontsParams = {},
+): Promise<ProxyFontsResponse> {
+    const queryString = buildQueryString(params);
+    const url = `${PROXY_API_URL}${queryString}`;
+
+    try {
+        const response = await api.get<ProxyFontsResponse>(url);
+        return response.data;
+    } catch (error) {
+        // Re-throw ApiError with context
+        if (error instanceof Error) {
+            throw error;
+        }
+        throw new Error(`Failed to fetch fonts from proxy API: ${String(error)}`);
+    }
+}
+
+/**
+ * Fetch font by ID
+ *
+ * Convenience function for fetching a single font by ID
+ * Note: This fetches a page and filters client-side, which is not ideal
+ * For production, consider adding a dedicated endpoint to the proxy API
+ *
+ * @param id - Font ID (family name for Google, slug for Fontshare)
+ * @returns Promise resolving to font or undefined
+ *
+ * @example
+ * ```ts
+ * const roboto = await fetchProxyFontById('Roboto');
+ * const satoshi = await fetchProxyFontById('satoshi');
+ * ```
+ */
+export async function fetchProxyFontById(
+    id: string,
+): Promise<UnifiedFont | undefined> {
+    const response = await fetchProxyFonts({ limit: 1000, q: id });
+    return response.fonts.find(font => font.id === id);
+}