Add N1 network tariff data with season/hour-based lookup

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

src/clj/pmagnus/elprice/web/controllers/tariffs.clj

@@ -0,0 +1,38 @@
+(ns pmagnus.elprice.web.controllers.tariffs
+  (:import
+   [java.time LocalDateTime]))
+
+(def n1-tariffs
+  "N1 network tariffs in øre/kWh (incl. VAT), effective 2026-01-01.
+   Source: https://n1.dk/elnetkunder/gaeldende-priser"
+  {:summer {:low  10.98   ;; 00:00-06:00
+            :high 16.47   ;; 06:00-17:00, 21:00-24:00
+            :peak 42.83}  ;; 17:00-21:00
+   :winter {:low  10.98
+            :high 32.95
+            :peak 98.84}})
+
+(defn season
+  "Returns :summer (Apr-Sep) or :winter (Oct-Mar) for a given month (1-12)."
+  [month]
+  (if (<= 4 month 9) :summer :winter))
+
+(defn load-level
+  "Returns :low, :high, or :peak for a given hour (0-23).
+   Low:  00:00-06:00
+   High: 06:00-17:00, 21:00-24:00
+   Peak: 17:00-21:00"
+  [hour]
+  (cond
+    (< hour 6)                      :low
+    (and (<= 6 hour) (< hour 17))   :high
+    (and (<= 17 hour) (< hour 21))  :peak
+    :else                           :high))
+
+(defn tariff-for-hour
+  "Returns the applicable N1 tariff in øre/kWh.
+   Can be called with (month, hour) or a LocalDateTime."
+  ([^LocalDateTime dt]
+   (tariff-for-hour (.getMonthValue dt) (.getHour dt)))
+  ([month hour]
+   (get-in n1-tariffs [(season month) (load-level hour)])))