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/preview/extract.ts

@@ -0,0 +1,111 @@
+import { execFile } from "child_process";
+import { promisify } from "util";
+import { childLogger } from "../util/logger.js";
+import type { FileEntry } from "../archive/zip-reader.js";
+
+const execFileAsync = promisify(execFile);
+const log = childLogger("preview-extract");
+
+/** Max bytes we'll accept for an extracted preview image (2MB). */
+const MAX_PREVIEW_BYTES = 2 * 1024 * 1024;
+
+/** Image extensions we consider valid previews, in priority order. */
+const IMAGE_EXTENSIONS = new Set(["jpg", "jpeg", "png"]);
+
+/**
+ * Pick the best preview image from the file entries list.
+ *
+ * Prefers files that look like dedicated preview images (01.jpg, insta.jpg,
+ * preview.jpg) over arbitrary images buried in subdirectories.
+ * Skips images that are suspiciously large (>2MB uncompressed).
+ */
+export function pickPreviewFile(entries: FileEntry[]): FileEntry | null {
+  const candidates = entries.filter((e) => {
+    if (!e.extension || !IMAGE_EXTENSIONS.has(e.extension.toLowerCase())) return false;
+    // Skip very large images — they're probably textures, not previews
+    if (e.uncompressedSize > BigInt(MAX_PREVIEW_BYTES)) return false;
+    return true;
+  });
+
+  if (candidates.length === 0) return null;
+
+  // Score candidates: lower depth + preview-like names win
+  const scored = candidates.map((entry) => {
+    const depth = entry.path.split("/").length - 1;
+    const nameLower = entry.fileName.toLowerCase();
+
+    let nameScore = 10; // default
+    // Known preview-like names get priority
+    if (/^(preview|thumb|cover|insta)\b/i.test(nameLower)) {
+      nameScore = 0;
+    } else if (/^0*[1-2]\.(jpe?g|png)$/i.test(nameLower)) {
+      // 01.jpg, 1.jpg, 02.jpg — common preview filenames
+      nameScore = 1;
+    } else if (/^0*[3-9]\.(jpe?g|png)$/i.test(nameLower)) {
+      nameScore = 2;
+    }
+
+    return { entry, score: nameScore + depth };
+  });
+
+  scored.sort((a, b) => a.score - b.score);
+  return scored[0].entry;
+}
+
+/**
+ * Extract a single file from an archive and return its contents as a Buffer.
+ *
+ * Uses the appropriate CLI tool based on archive type:
+ * - ZIP: unzip -p
+ * - RAR: unrar p -inul
+ * - 7Z: 7z e -so
+ */
+export async function extractPreviewImage(
+  archivePath: string,
+  archiveType: "ZIP" | "RAR" | "SEVEN_Z" | "DOCUMENT",
+  filePath: string
+): Promise<Buffer | null> {
+  if (archiveType === "DOCUMENT") return null;
+
+  try {
+    let stdout: Buffer;
+
+    if (archiveType === "ZIP") {
+      const result = await execFileAsync("unzip", ["-p", archivePath, filePath], {
+        timeout: 15000,
+        maxBuffer: MAX_PREVIEW_BYTES,
+        encoding: "buffer",
+      });
+      stdout = result.stdout as unknown as Buffer;
+    } else if (archiveType === "RAR") {
+      const result = await execFileAsync("unrar", ["p", "-inul", archivePath, filePath], {
+        timeout: 15000,
+        maxBuffer: MAX_PREVIEW_BYTES,
+        encoding: "buffer",
+      });
+      stdout = result.stdout as unknown as Buffer;
+    } else {
+      // SEVEN_Z
+      const result = await execFileAsync("7z", ["e", "-so", archivePath, filePath], {
+        timeout: 15000,
+        maxBuffer: MAX_PREVIEW_BYTES,
+        encoding: "buffer",
+      });
+      stdout = result.stdout as unknown as Buffer;
+    }
+
+    if (stdout.length === 0) {
+      log.warn({ archivePath, filePath }, "Extracted preview image is empty");
+      return null;
+    }
+
+    log.debug(
+      { archivePath, filePath, bytes: stdout.length },
+      "Extracted preview image from archive"
+    );
+    return stdout;
+  } catch (err) {
+    log.warn({ err, archivePath, filePath }, "Failed to extract preview image from archive");
+    return null;
+  }
+}