Add batch cleaning with per-file review and ZIP download

Up to 50 images at once; single-image flow unchanged. Includes a
dependency-free stored-ZIP writer.

Co-Authored-By: Claude Sonnet 5.5 <noreply@anthropic.com>

src/lib/zip.js

@@ -0,0 +1,90 @@
+/**
+ * Minimal ZIP writer (stored, no compression). Images are already compressed,
+ * so deflating them gains nothing, and this avoids a dependency.
+ */
+
+const CRC_TABLE = (() => {
+  const table = new Uint32Array(256);
+  for (let n = 0; n < 256; n++) {
+    let c = n;
+    for (let k = 0; k < 8; k++) c = c & 1 ? 0xedb88320 ^ (c >>> 1) : c >>> 1;
+    table[n] = c >>> 0;
+  }
+  return table;
+})();
+
+function crc32(bytes) {
+  let crc = 0xffffffff;
+  for (let i = 0; i < bytes.length; i++) {
+    crc = CRC_TABLE[(crc ^ bytes[i]) & 0xff] ^ (crc >>> 8);
+  }
+  return (crc ^ 0xffffffff) >>> 0;
+}
+
+function header(size, write) {
+  const view = new DataView(new ArrayBuffer(size));
+  write(view);
+  return new Uint8Array(view.buffer);
+}
+
+/** @param {{name: string, data: Uint8Array}[]} files @returns {Blob} */
+export function createZip(files) {
+  const encoder = new TextEncoder();
+  const now = new Date();
+  const time = (now.getHours() << 11) | (now.getMinutes() << 5) | (now.getSeconds() >> 1);
+  const date = ((now.getFullYear() - 1980) << 9) | ((now.getMonth() + 1) << 5) | now.getDate();
+
+  const parts = [];
+  const central = [];
+  let offset = 0;
+
+  for (const { name, data } of files) {
+    const nameBytes = encoder.encode(name);
+    const crc = crc32(data);
+
+    const local = header(30, (v) => {
+      v.setUint32(0, 0x04034b50, true);
+      v.setUint16(4, 20, true);
+      v.setUint16(6, 0x0800, true); // UTF-8 names
+      v.setUint16(8, 0, true); // stored
+      v.setUint16(10, time, true);
+      v.setUint16(12, date, true);
+      v.setUint32(14, crc, true);
+      v.setUint32(18, data.length, true);
+      v.setUint32(22, data.length, true);
+      v.setUint16(26, nameBytes.length, true);
+    });
+    parts.push(local, nameBytes, data);
+
+    central.push(
+      header(46, (v) => {
+        v.setUint32(0, 0x02014b50, true);
+        v.setUint16(4, 20, true);
+        v.setUint16(6, 20, true);
+        v.setUint16(8, 0x0800, true);
+        v.setUint16(10, 0, true);
+        v.setUint16(12, time, true);
+        v.setUint16(14, date, true);
+        v.setUint32(16, crc, true);
+        v.setUint32(20, data.length, true);
+        v.setUint32(24, data.length, true);
+        v.setUint16(28, nameBytes.length, true);
+        v.setUint32(42, offset, true);
+      }),
+      nameBytes
+    );
+
+    offset += local.length + nameBytes.length + data.length;
+  }
+
+  const centralSize = central.reduce((sum, part) => sum + part.length, 0);
+  const end = header(22, (v) => {
+    v.setUint32(0, 0x06054b50, true);
+    v.setUint16(8, files.length, true);
+    v.setUint16(10, files.length, true);
+    v.setUint32(12, centralSize, true);
+    v.setUint32(16, offset, true);
+  });
+
+  return new Blob([...parts, ...central, end], { type: "application/zip" });
+}