Add fetch timeout/retry, friendly error messages, and VAT rate constant

- fetchWithTimeout (10s) + fetchWithRetry (3 attempts, exponential backoff)
- DataError class with type classification (config/network/auth/timeout/unknown)
- User-friendly error messages in EN/AR instead of raw error strings
- Extract VAT_RATE constant (was hardcoded 1.15)

Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>

src/services/dataService.ts

@@ -14,26 +14,70 @@ import type {
   UmrahData,
   NocoDBDistrict,
   NocoDBMuseum,
-  NocoDBDailyStat
+  NocoDBDailyStat,
+  DataErrorType
 } from '../types';
+import { DataError } from '../types';
 
 const NOCODB_URL = import.meta.env.VITE_NOCODB_URL || '';
 const NOCODB_TOKEN = import.meta.env.VITE_NOCODB_TOKEN || '';
 const NOCODB_BASE_ID = import.meta.env.VITE_NOCODB_BASE_ID || '';
 
+const FETCH_TIMEOUT_MS = 10_000;
+const MAX_RETRIES = 3;
+const VAT_RATE = 1.15;
+
 // Table IDs discovered dynamically from NocoDB meta API
 let discoveredTables: Record<string, string> | null = null;
 
+// ============================================
+// Fetch Helpers (timeout + retry)
+// ============================================
+
+async function fetchWithTimeout(url: string, options: RequestInit = {}, timeoutMs: number = FETCH_TIMEOUT_MS): Promise<Response> {
+  const controller = new AbortController();
+  const timer = setTimeout(() => controller.abort(), timeoutMs);
+  try {
+    const res = await fetch(url, { ...options, signal: controller.signal });
+    return res;
+  } catch (err) {
+    if ((err as Error).name === 'AbortError') {
+      throw new Error(`Request timed out after ${timeoutMs}ms`);
+    }
+    throw err;
+  } finally {
+    clearTimeout(timer);
+  }
+}
+
+async function fetchWithRetry(url: string, options: RequestInit = {}, retries: number = MAX_RETRIES): Promise<Response> {
+  let lastError: Error | null = null;
+  for (let attempt = 0; attempt < retries; attempt++) {
+    try {
+      const res = await fetchWithTimeout(url, options);
+      if (!res.ok) throw new Error(`HTTP ${res.status}`);
+      return res;
+    } catch (err) {
+      lastError = err as Error;
+      if (attempt < retries - 1) {
+        const delay = Math.pow(2, attempt) * 1000; // 1s, 2s, 4s
+        console.warn(`Fetch attempt ${attempt + 1} failed, retrying in ${delay}ms...`);
+        await new Promise(r => setTimeout(r, delay));
+      }
+    }
+  }
+  throw lastError;
+}
+
 async function discoverTableIds(): Promise<Record<string, string>> {
   if (discoveredTables) return discoveredTables;
 
   if (!NOCODB_BASE_ID) throw new Error('VITE_NOCODB_BASE_ID not configured');
 
-  const res = await fetch(
+  const res = await fetchWithRetry(
     `${NOCODB_URL}/api/v2/meta/bases/${NOCODB_BASE_ID}/tables`,
     { headers: { 'xc-token': NOCODB_TOKEN } }
   );
-  if (!res.ok) throw new Error(`Failed to discover tables: HTTP ${res.status}`);
 
   const json = await res.json();
   const tables: Record<string, string> = {};
@@ -71,8 +115,7 @@ export async function fetchPilgrimStats(): Promise<UmrahData> {
       return umrahData;
     }
     const url = `${NOCODB_URL}/api/v2/tables/${tables['PilgrimStats']}/records?limit=50`;
-    const res = await fetch(url, { headers: { 'xc-token': NOCODB_TOKEN } });
-    if (!res.ok) throw new Error(`HTTP ${res.status}`);
+    const res = await fetchWithRetry(url, { headers: { 'xc-token': NOCODB_TOKEN } });
     const json = await res.json();
     const records = json.list || [];
     
@@ -165,15 +208,13 @@ export function clearCache(): void {
 async function fetchNocoDBTable<T>(tableId: string, limit: number = 1000): Promise<T[]> {
   let allRecords: T[] = [];
   let offset = 0;
-  
+
   while (true) {
-    const response = await fetch(
+    const response = await fetchWithRetry(
       `${NOCODB_URL}/api/v2/tables/${tableId}/records?limit=${limit}&offset=${offset}`,
       { headers: { 'xc-token': NOCODB_TOKEN } }
     );
     
-    if (!response.ok) throw new Error(`HTTP ${response.status}`);
-    
     const json = await response.json();
     const records: T[] = json.list || [];
     allRecords = allRecords.concat(records);
@@ -226,7 +267,7 @@ async function fetchFromNocoDB(): Promise<MuseumRecord[]> {
     
     // GrossRevenue = including VAT, NetRevenue = excluding VAT
     const grossRevenue = row.GrossRevenue || 0;
-    const netRevenue = row.NetRevenue || (grossRevenue / 1.15);
+    const netRevenue = row.NetRevenue || (grossRevenue / VAT_RATE);
     
     return {
       date: date,
@@ -247,6 +288,19 @@ async function fetchFromNocoDB(): Promise<MuseumRecord[]> {
   return data;
 }
 
+// ============================================
+// Error Classification
+// ============================================
+
+function classifyError(err: Error): DataErrorType {
+  const msg = err.message.toLowerCase();
+  if (msg.includes('not configured')) return 'config';
+  if (msg.includes('timed out') || msg.includes('timeout')) return 'timeout';
+  if (msg.includes('401') || msg.includes('403') || msg.includes('authentication') || msg.includes('unauthorized')) return 'auth';
+  if (msg.includes('failed to fetch') || msg.includes('network') || msg.includes('econnrefused') || msg.includes('err_connection')) return 'network';
+  return 'unknown';
+}
+
 // ============================================
 // Main Data Fetcher (with offline fallback)
 // ============================================
@@ -254,34 +308,29 @@ async function fetchFromNocoDB(): Promise<MuseumRecord[]> {
 export async function fetchData(): Promise<FetchResult> {
   // Check if NocoDB is configured
   if (!NOCODB_URL || !NOCODB_TOKEN || !NOCODB_BASE_ID) {
-    // Try cache
     const cached = loadFromCache();
     if (cached) {
       console.warn('NocoDB not configured, using cached data');
       return { data: cached.data, fromCache: true, cacheTimestamp: cached.timestamp };
     }
-    throw new Error('NocoDB not configured and no cached data available. Set VITE_NOCODB_URL, VITE_NOCODB_TOKEN, and VITE_NOCODB_BASE_ID in .env.local');
+    throw new DataError('NocoDB not configured', 'config');
   }
-  
+
   try {
-    // Try to fetch fresh data
     const data = await fetchFromNocoDB();
-    
-    // Save to cache on success
     saveToCache(data);
-    
     return { data, fromCache: false };
   } catch (err) {
     console.error('NocoDB fetch failed:', (err as Error).message);
-    
-    // Try to load from cache
+
     const cached = loadFromCache();
     if (cached) {
       console.warn(`Using cached data from ${new Date(cached.timestamp).toLocaleString()} (offline mode)`);
       return { data: cached.data, fromCache: true, cacheTimestamp: cached.timestamp };
     }
-    
-    throw new Error(`Database unavailable and no cached data: ${(err as Error).message}`);
+
+    const errorType = classifyError(err as Error);
+    throw new DataError((err as Error).message, errorType);
   }
 }