Add GW webshop catalog source (Algolia): dlphelper.gwshop + full dump

- warhammer.com shop HTML/listing endpoints are behind AWS WAF (405/202
  goku challenge) for non-browser clients; findings recorded in AGENTS.md
- the shop search runs on Algolia; public search-only key lets us dump the
  whole product index with plain requests (no browser, no captcha)
- gwshop.py: credential loading (env or gitignored algolia.json), index
  listing, facet-partitioned full retrieval (search-only key cannot /browse
  and pagination caps at 1000, so the index is partitioned on the
  GameSystemsRoot hierarchy facet), normalization into the sorter's
  source-agnostic catalog schema (system/group/faction/subfaction/class)
- data/gwshop_catalog.json: snapshot of prod-lazarus-product-en-ww,
  3491 unique products, every product with full hierarchy path
- tools/: one-shot browse + catalog builder + shape inspector

.gitignore

@@ -18,3 +18,7 @@ manifest.jsonl
 # Never commit credentials
 *.token
 .env
+
+# Algolia credentials (search-only key, still never commit)
+algolia.json
+gwshop_raw.json