Fix: delete file issues

fyo/model/attachmentEncoding.ts

@@ -0,0 +1,42 @@
+function uint8ArrayToBase64(bytes: Uint8Array): string | null {
+  try {
+    // Browser/Electron renderer
+    // eslint-disable-next-line no-undef
+    if (typeof btoa === 'function') {
+      let binary = '';
+      const chunkSize = 0x8000;
+      for (let i = 0; i < bytes.length; i += chunkSize) {
+        binary += String.fromCharCode(...bytes.subarray(i, i + chunkSize));
+      }
+      // eslint-disable-next-line no-undef
+      return btoa(binary);
+    }
+  } catch (err) {
+    // best-effort; fallback to Buffer path below
+    console.warn(
+      '[books] attachment encoding failed using btoa/String.fromCharCode',
+      err
+    );
+  }
+
+  // Fallback (Node-like)
+  const B = (globalThis as { Buffer?: typeof Buffer | undefined })?.Buffer;
+  if (B) {
+    try {
+      return B.from(bytes).toString('base64');
+    } catch (err) {
+      console.warn('[books] attachment encoding failed using Buffer', err);
+      return null;
+    }
+  }
+  return null;
+}
+
+export function dataUrlFromBytes(type: string, bytes: Uint8Array): string | null {
+  const base64 = uint8ArrayToBase64(bytes);
+  if (!base64) {
+    return null;
+  }
+  return `data:${type || 'application/octet-stream'};base64,${base64}`;
+}
+