docs(amazon): add module status readme

surfsense_backend/app/proprietary/platforms/amazon/README.md

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+# Amazon Product Scraper
+
+Current status: product details, search and category discovery, offers, sellers,
+best-seller rankings, on-page reviews, localized delivery sessions, and product
+variants are implemented. The `amazon.scrape` capability exposes the scraper
+with per-product billing and a hard per-run result ceiling.
+
+## Scope
+
+The scraper reads public pages available to anonymous visitors. It does not log
+in, use account cookies, or retrieve account-gated content. Delivery
+localization uses an anonymous session cookie pinned to the same proxy exit.
+
+Deep review pagination currently requires an account on Amazon and is therefore
+out of scope. Reviews embedded in a public product page are returned in
+`productPageReviews` and `productPageReviewsFromOtherCountries`.
+
+## Architecture
+
+- `schemas.py` defines the stable input, product, and error models.
+- `url_resolver.py` classifies product, search, best-sellers, and shortened URLs.
+- `fetch.py` owns proxy-aware HTTP access, block detection, retries, and
+  anonymous location sessions.
+- `parsers.py` contains pure, defensive HTML parsers.
+- `scraper.py` coordinates discovery, enrichment, concurrency, limits, and
+  in-stream errors.
+
+## Implementation progress
+
+- Done: public product detail parsing and shortened-link dispatch.
+- Done: search/category paging with card-only and detailed modes.
+- Done: public offers and seller enrichment.
+- Done: best-seller rankings and product-page reviews.
+- Done: anonymous localized delivery sessions on sticky proxy exits.
+- Done: variant expansion, variant prices, capability registration, and billing.
+
+## Verification
+
+Offline fixtures cover every parser and flow:
+
+```bash
+cd surfsense_backend
+uv run pytest tests/unit/platforms/amazon tests/unit/capabilities/amazon
+```
+
+The manual live check requires proxy credentials:
+
+```bash
+uv run python scripts/e2e_amazon_scraper.py
+```