feat(worker): auto-tag packages with the slicer(s) their files target

Indexes 86k+ Lychee Slicer (.lys/.lyt), 23k+ ChituBox (.chitubox/.ctb/
.cbddlp), 1k+ Anycubic (.photon/.pwmo/.pwmx), and Bambu (.3mf)
slicer-specific files. Until now they were just generic extensions in
PackageFile.

After this commit:
  - Newly-ingested packages get tags derived from their file list
    ("lychee", "chitubox", "anycubic", "bambu", "fdm", "mango")
  - The `backfill_filelists` listener also applies tags to re-indexed
    packages
  - A new pure-DB listener `backfill_slicer_tags` walks existing
    Packages with file lists and applies tags retroactively — no
    downloads, no TDLib, takes seconds for thousands of rows.

Trigger the one-shot retroactive backfill with:
  SELECT pg_notify('backfill_slicer_tags', '{"limit":5000}');

Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>

worker/src/archive/slicer-tags.ts

@@ -0,0 +1,58 @@
+import type { FileEntry } from "./zip-reader.js";
+
+/**
+ * Mapping from file extensions to slicer tags. Each tag groups a family of
+ * extensions that mean the same thing for end users — "this archive contains
+ * files I can open in <slicer>".
+ *
+ * Extensions are matched case-insensitively without the leading dot.
+ */
+const SLICER_EXTENSION_MAP: Record<string, string> = {
+  // Lychee Slicer
+  lys: "lychee",
+  lyt: "lychee",
+  lyc: "lychee",
+
+  // ChituBox / Anycubic / Phrozen / Elegoo (resin printers)
+  chitubox: "chitubox",
+  ctb: "chitubox",
+  cbddlp: "chitubox",
+
+  // Anycubic Photon family
+  photon: "anycubic",
+  pwmo: "anycubic",
+  pwmx: "anycubic",
+  pwmb: "anycubic",
+  pwma: "anycubic",
+  pws: "anycubic",
+  pwsq: "anycubic",
+  phz: "anycubic",
+
+  // Bambu / Prusa
+  "3mf": "bambu",
+  bgcode: "bambu",
+
+  // FDM gcode (generic)
+  gcode: "fdm",
+
+  // Mango / generic resin formats sometimes seen in releases
+  mfp: "mango",
+  mfpv: "mango",
+  osla: "mango",
+};
+
+/**
+ * Derive a deduplicated list of slicer tags from an archive's file listing.
+ * Returns an empty array if no recognised slicer-specific files are present
+ * (e.g., the archive is just STLs without pre-supports).
+ */
+export function extractSlicerTags(entries: FileEntry[]): string[] {
+  const tags = new Set<string>();
+  for (const entry of entries) {
+    if (!entry.extension) continue;
+    const ext = entry.extension.toLowerCase();
+    const tag = SLICER_EXTENSION_MAP[ext];
+    if (tag) tags.add(tag);
+  }
+  return [...tags].sort();
+}