ICE aging + by-port: serving models, API endpoints, dashboard integration

- serving/ice_aging_stocks.sql: pass-through from foundation, parses age
  bucket string to start/end days ints for correct sort order
- serving/ice_warehouse_stocks_by_port.sql: monthly by-port since 1996,
  adds MoM change, MoM %, 12-month rolling average
- analytics.py: get_ice_aging_latest(), get_ice_aging_trend(),
  get_ice_stocks_by_port_trend(), get_ice_stocks_by_port_latest()
- api/routes.py: GET /commodities/<code>/stocks/aging and
  GET /commodities/<code>/stocks/by-port with auth + rate limiting
- dashboard/routes.py: add 3 new queries to asyncio.gather(), pass to template
- index.html: aging stacked bar chart (age buckets × port) with 4 metric
  cards; by-port stacked area chart (30-year history) with 4 metric cards

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

transform/sqlmesh_materia/models/serving/ice_aging_stocks.sql

@@ -0,0 +1,60 @@
+-- Serving mart: ICE certified Coffee C stock aging report, analytics-ready.
+--
+-- Shows the age distribution of certified stocks across delivery ports.
+-- Age buckets represent how long coffee has been in certified storage.
+-- Older stock approaching certificate limits is a supply quality signal.
+--
+-- Source: ICE Certified Stock Aging Report (monthly)
+-- Grain: one row per (report_date, age_bucket).
+
+MODEL (
+  name serving.ice_aging_stocks,
+  kind INCREMENTAL_BY_TIME_RANGE (
+    time_column report_date
+  ),
+  grain (report_date, age_bucket),
+  start '2020-01-01',
+  cron '@daily'
+);
+
+WITH base AS (
+  SELECT
+    f.report_date,
+    f.age_bucket,
+
+    -- Parse age range from "0000 to 0120" format for correct sort order
+    TRY_CAST(split_part(f.age_bucket, ' to ', 1) AS int) AS age_bucket_start_days,
+    TRY_CAST(split_part(f.age_bucket, ' to ', 2) AS int) AS age_bucket_end_days,
+
+    f.antwerp_bags,
+    f.hamburg_bremen_bags,
+    f.houston_bags,
+    f.miami_bags,
+    f.new_orleans_bags,
+    f.new_york_bags,
+    f.total_bags,
+
+    f.source_file
+  FROM foundation.fct_ice_aging_stocks f
+  WHERE f.report_date BETWEEN @start_ds AND @end_ds
+)
+
+SELECT
+  b.report_date,
+  d.commodity_name,
+  d.ice_stock_report_code,
+  b.age_bucket,
+  b.age_bucket_start_days,
+  b.age_bucket_end_days,
+  b.antwerp_bags,
+  b.hamburg_bremen_bags,
+  b.houston_bags,
+  b.miami_bags,
+  b.new_orleans_bags,
+  b.new_york_bags,
+  b.total_bags,
+  b.source_file
+FROM base b
+CROSS JOIN foundation.dim_commodity d
+WHERE d.ice_stock_report_code = 'COFFEE-C'
+ORDER BY b.report_date, b.age_bucket_start_days