feat(proxy): per-proxy dead tracking in tiered cycler

Add proxy_failure_limit param to make_tiered_cycler (default 3).
Individual proxies hitting the limit are marked dead and permanently
skipped. next_proxy() auto-escalates when all proxies in the active
tier are dead. Both mechanisms coexist: per-proxy dead tracking removes
broken individuals; tier-level threshold catches systemic failure.

- proxy.py: dead_proxies set + proxy_failure_counts dict in state;
  next_proxy skips dead proxies with bounded loop; record_failure/
  record_success accept optional proxy_url; dead_proxy_count() added
- playtomic_tenants.py: pass proxy_url to record_success/record_failure
- playtomic_availability.py: _worker returns (proxy_url, result);
  serial loops in extract + extract_recheck capture proxy_url
- test_supervisor.py: 11 new tests in TestTieredCyclerDeadProxyTracking

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

CHANGELOG.md

@@ -6,6 +6,13 @@ The format is based on [Keep a Changelog](https://keepachangelog.com/en/1.1.0/).
 
 ## [Unreleased]
 
+### Changed
+- **Per-proxy dead tracking in tiered cycler** — `make_tiered_cycler` now accepts a `proxy_failure_limit` parameter (default 3). Individual proxies that hit the limit are marked dead and permanently skipped by `next_proxy()`. If all proxies in the active tier are dead, `next_proxy()` auto-escalates to the next tier without needing the tier-level threshold. `record_failure(proxy_url)` and `record_success(proxy_url)` accept an optional `proxy_url` argument for per-proxy tracking; callers without `proxy_url` are fully backward-compatible. New `dead_proxy_count()` callable exposed for monitoring.
+  - `extract/padelnomics_extract/src/padelnomics_extract/proxy.py`: added per-proxy state (`proxy_failure_counts`, `dead_proxies`), updated `next_proxy`/`record_failure`/`record_success`, added `dead_proxy_count`
+  - `extract/padelnomics_extract/src/padelnomics_extract/playtomic_tenants.py`: `_fetch_page_via_cycler` passes `proxy_url` to `record_success`/`record_failure`
+  - `extract/padelnomics_extract/src/padelnomics_extract/playtomic_availability.py`: `_worker` returns `(proxy_url, result)` tuple; serial loops in `extract` and `extract_recheck` capture `proxy_url` before passing to `record_success`/`record_failure`
+  - `web/tests/test_supervisor.py`: 11 new tests in `TestTieredCyclerDeadProxyTracking` covering dead proxy skipping, auto-escalation, `dead_proxy_count`, backward compat, and thread safety
+
 ### Added
 - **Affiliate programs management** — centralised retailer config (`affiliate_programs` table) with URL template + tracking tag + commission %. Products now use a program dropdown + product identifier (e.g. ASIN) instead of manually baking full URLs. URL is assembled at redirect time via `build_affiliate_url()`, so changing a tag propagates instantly to all products. Legacy products (baked `affiliate_url`) continue to work via fallback. Amazon OneLink configured in the Associates dashboard handles geo-redirect to local marketplaces — no per-country programs needed.
   - `web/src/padelnomics/migrations/versions/0027_affiliate_programs.py`: `affiliate_programs` table, nullable `program_id` + `product_identifier` columns on `affiliate_products`, seeds "Amazon" program, backfills ASINs from existing URLs