Chore: Restructure Repository for SvelteKit

_old/core/async/fetchWithRetry.ts

@@ -0,0 +1,31 @@
+export interface RetryOptions {
+  maxAttempts?: number;
+  baseDelayMs?: number;
+  maxDelayMs?:  number;
+  shouldRetry?: (err: unknown, attempt: number) => boolean;
+}
+
+export async function fetchWithRetry<T>(
+  fetcher: () => Promise<T>,
+  options: RetryOptions = {},
+): Promise<T> {
+  const {
+    maxAttempts = 3,
+    baseDelayMs = 500,
+    maxDelayMs  = 10_000,
+    shouldRetry = () => true,
+  } = options;
+
+  let lastErr: unknown;
+  for (let attempt = 1; attempt <= maxAttempts; attempt++) {
+    try {
+      return await fetcher();
+    } catch (err) {
+      lastErr = err;
+      if (attempt === maxAttempts || !shouldRetry(err, attempt)) throw err;
+      const delay = Math.min(baseDelayMs * 2 ** (attempt - 1), maxDelayMs);
+      await new Promise(r => setTimeout(r, delay));
+    }
+  }
+  throw lastErr;
+}