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>

transform/sqlmesh_materia/models/raw/ice_aging_stocks.sql

@@ -0,0 +1,49 @@
+-- Raw ICE certified stock aging report — technical ingestion layer.
+--
+-- Reads monthly aging report gzip CSVs from the landing directory.
+-- All values are varchar; casting happens in foundation.fct_ice_aging_stocks.
+--
+-- Source: ICE Report Center (Certified Stock Aging Report)
+-- Coverage: varies by download history
+-- Frequency: monthly (ICE updates after each delivery month)
+
+MODEL (
+  name raw.ice_aging_stocks,
+  kind FULL,
+  cron '@daily',
+  columns (
+    report_date             varchar,
+    age_bucket              varchar,
+    antwerp_bags            varchar,
+    hamburg_bremen_bags     varchar,
+    houston_bags            varchar,
+    miami_bags              varchar,
+    new_orleans_bags        varchar,
+    new_york_bags           varchar,
+    total_bags              varchar,
+    filename                varchar
+  )
+);
+
+SELECT
+  report_date,
+  age_bucket,
+  antwerp_bags,
+  hamburg_bremen_bags,
+  houston_bags,
+  miami_bags,
+  new_orleans_bags,
+  new_york_bags,
+  total_bags,
+  filename
+FROM read_csv(
+  @ice_aging_glob(),
+  delim = ',',
+  encoding = 'utf-8',
+  compression = 'gzip',
+  header = true,
+  union_by_name = true,
+  filename = true,
+  all_varchar = true,
+  ignore_errors = true
+)

transform/sqlmesh_materia/models/raw/ice_warehouse_stocks_by_port.sql

@@ -0,0 +1,51 @@
+-- Raw ICE historical end-of-month warehouse stocks by port — technical ingestion layer.
+--
+-- Reads historical by-port stock gzip CSVs from the landing directory.
+-- All values are varchar; casting happens in foundation.fct_ice_warehouse_stocks_by_port.
+--
+-- Source: ICE (EOM_KC_cert_stox_by_port_nov96-present.xls)
+-- Coverage: November 1996 to present
+-- Frequency: monthly (ICE updates the static file monthly)
+
+MODEL (
+  name raw.ice_warehouse_stocks_by_port,
+  kind FULL,
+  cron '@daily',
+  columns (
+    report_date             varchar,
+    new_york_bags           varchar,
+    new_orleans_bags        varchar,
+    houston_bags            varchar,
+    miami_bags              varchar,
+    antwerp_bags            varchar,
+    hamburg_bremen_bags     varchar,
+    barcelona_bags          varchar,
+    virginia_bags           varchar,
+    total_bags              varchar,
+    filename                varchar
+  )
+);
+
+SELECT
+  report_date,
+  new_york_bags,
+  new_orleans_bags,
+  houston_bags,
+  miami_bags,
+  antwerp_bags,
+  hamburg_bremen_bags,
+  barcelona_bags,
+  virginia_bags,
+  total_bags,
+  filename
+FROM read_csv(
+  @ice_stocks_by_port_glob(),
+  delim = ',',
+  encoding = 'utf-8',
+  compression = 'gzip',
+  header = true,
+  union_by_name = true,
+  filename = true,
+  all_varchar = true,
+  ignore_errors = true
+)