feat: add preview management, channel controls, invite polish, and recovery

- Auto-extract preview images from ZIP/RAR/7z archives during ingestion
- Upload custom preview images via package drawer
- Select preview from archive contents with on-demand extraction UI
- Manually add Telegram channels by t.me link, username, or invite link
- Invite code UX: bulk create, copy link, usage tracking, delete confirm
- Incomplete upload recovery: verify dest messages on worker startup
- Rebuild package DB by scanning destination channel with live progress

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

worker/src/archive/extract-image.ts

@@ -0,0 +1,33 @@
+import path from "path";
+
+const IMAGE_EXTENSIONS = new Set(["jpg", "jpeg", "png", "webp", "gif", "bmp"]);
+
+/**
+ * Check if a file path within an archive is an image.
+ */
+export function isImageFile(filePath: string): boolean {
+  const ext = path.extname(filePath).toLowerCase().slice(1);
+  return IMAGE_EXTENSIONS.has(ext);
+}
+
+/**
+ * Get the MIME type for an image file extension.
+ */
+export function getImageMimeType(filePath: string): string {
+  const ext = path.extname(filePath).toLowerCase().slice(1);
+  switch (ext) {
+    case "jpg":
+    case "jpeg":
+      return "image/jpeg";
+    case "png":
+      return "image/png";
+    case "webp":
+      return "image/webp";
+    case "gif":
+      return "image/gif";
+    case "bmp":
+      return "image/bmp";
+    default:
+      return "application/octet-stream";
+  }
+}