Add elprice table + JSON API (GET /api/elprice?date=...)

New `elprice` table with a simpler shape (time_dk, price_area,
price_dkk) backing a JSON endpoint that returns hourly DK1 + DK2
prices for any date. Cache-miss path fetches from the same
DayAheadPrices dataset as day_ahead_prices, upserts, and returns.

Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>

resources/migrations/20260419010000-create-elprice.down.sql

@@ -0,0 +1 @@
+DROP TABLE elprice;

resources/migrations/20260419010000-create-elprice.up.sql

@@ -0,0 +1,6 @@
+CREATE TABLE elprice (
+  time_dk    TIMESTAMP     NOT NULL,
+  price_area VARCHAR(3)    NOT NULL,
+  price_dkk  NUMERIC(10,2) NOT NULL,
+  PRIMARY KEY (time_dk, price_area)
+);

resources/queries.sql

@@ -65,3 +65,16 @@ ON CONFLICT (time_start, hour) DO NOTHING;
 INSERT INTO consumption (time_start, hour, kwh)
 VALUES (:time-start, :hour, :kwh)
 ON CONFLICT (time_start, hour) DO NOTHING;
+
+-- :name insert-elprice! :! :n
+-- :doc Insert an hourly el-price row; keep first value on conflict
+INSERT INTO elprice (time_dk, price_area, price_dkk)
+VALUES (:time-dk, :price-area, :price-dkk)
+ON CONFLICT (time_dk, price_area) DO NOTHING;
+
+-- :name get-elprice-for-date :? :*
+-- :doc Hourly prices for a DK local date, both areas
+SELECT time_dk, price_area, price_dkk
+FROM elprice
+WHERE time_dk::date = :date
+ORDER BY time_dk, price_area;