Fetch and display day-ahead electricity spot prices from Energi Data Service

Adds a prices controller that fetches DK1/DK2 hourly spot prices via the
Energi Data Service API, stores them in PostgreSQL, and displays today's
and tomorrow's DK1 prices on the home page in øre/kWh. An HTMX "Refresh
Prices" button triggers the fetch-and-display cycle.

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

resources/migrations/20260214120000-create-day-ahead-prices.down.sql

@@ -0,0 +1 @@
+DROP TABLE IF EXISTS day_ahead_prices;

resources/migrations/20260214120000-create-day-ahead-prices.up.sql

@@ -0,0 +1,8 @@
+CREATE TABLE day_ahead_prices (
+  time_utc       TIMESTAMPTZ NOT NULL,
+  time_dk        TIMESTAMP   NOT NULL,
+  price_area     VARCHAR(3)  NOT NULL,
+  price_dkk      NUMERIC(10,2),
+  price_eur      NUMERIC(10,6),
+  PRIMARY KEY (time_utc, price_area)
+);

resources/queries.sql

@@ -1,2 +1,16 @@
--- place your sql queries here
--- see https://www.hugsql.org/ for documentation
+-- :name upsert-price! :! :n
+-- :doc Upsert a day-ahead price record
+INSERT INTO day_ahead_prices (time_utc, time_dk, price_area, price_dkk, price_eur)
+VALUES (:time-utc, :time-dk, :price-area, :price-dkk, :price-eur)
+ON CONFLICT (time_utc, price_area) DO UPDATE
+SET time_dk = EXCLUDED.time_dk,
+    price_dkk = EXCLUDED.price_dkk,
+    price_eur = EXCLUDED.price_eur;
+
+-- :name get-prices-for-date :? :*
+-- :doc Get all prices for a given date (time_dk local date) and price area
+SELECT time_utc, time_dk, price_area, price_dkk, price_eur
+FROM day_ahead_prices
+WHERE time_dk::date = :date
+  AND price_area = :price-area
+ORDER BY time_dk;

resources/system.edn

@@ -66,4 +66,5 @@
   :db {:datasource #ig/ref :db.sql/connection}
   :migrate-on-init? true}
  :reitit.routes/ui {:base-path "",
-                    :env #ig/ref :system/env}}
+                    :env #ig/ref :system/env
+                    :query-fn #ig/ref :db.sql/query-fn}}