ICE extraction overhaul: API discovery + aging report + historical backfill

- Replace brittle ICE_STOCKS_URL env var with API-based URL discovery via
  the private ICE Report Center JSON API (no auth required)
- Add rolling CSV → XLS fallback in extract_ice_stocks() using
  find_latest_report() from ice_api.py
- Add ice_api.py: fetch_report_listings(), find_latest_report() with
  pagination up to MAX_API_PAGES
- Add xls_parse.py: detect_file_format() (magic bytes), xls_to_rows()
  using xlrd for OLE2/BIFF XLS files
- Add extract_ice_aging(): monthly certified stock aging report by
  age bucket × port → ice_aging/ landing dir
- Add extract_ice_historical(): 30-year EOM by-port stocks from static
  ICE URL → ice_stocks_by_port/ landing dir
- Add xlrd>=2.0.1 (parse XLS), xlwt>=1.3.0 (dev, test fixtures)
- Add SQLMesh raw + foundation models for both new datasets
- Add ice_aging_glob(), ice_stocks_by_port_glob() macros
- Add extract_ice_aging + extract_ice_historical pipeline entries
- Add 12 unit tests (format detection, XLS roundtrip, API mock, CSV output)

Seed files (data/landing/ice_aging/seed/ and ice_stocks_by_port/seed/)
must be created locally — data/ is gitignored.

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

extract/ice_stocks/pyproject.toml

@@ -5,10 +5,13 @@ description = "ICE certified warehouse stocks extractor"
 requires-python = ">=3.13"
 dependencies = [
     "niquests>=3.14.1",
+    "xlrd>=2.0.1",
 ]
 
 [project.scripts]
 extract_ice = "ice_stocks.execute:extract_ice_stocks"
+extract_ice_aging = "ice_stocks.execute:extract_ice_aging"
+extract_ice_historical = "ice_stocks.execute:extract_ice_historical"
 
 [build-system]
 requires = ["hatchling"]