Fix Frankfurter integration: require namespace, use v1 API, show converted BTC prices

- Require frankfurter.rates namespace in core.clj so Integrant can find it
- Use /v1/ prefix for self-hosted Frankfurter API
- Display BTC price converted to EUR and DKK instead of raw exchange rates
- Remove unused host port mapping for Frankfurter container

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

src/clj/pmagnus/btcdata/web/routes/api.clj

@@ -23,8 +23,8 @@
    (cond-> {:price       (str price)
             :prev_price  (when prev-price (str prev-price))
             :recorded_at (str recorded-at)}
-     rates (assoc :eur (str (:eur rates))
-                  :dkk (str (:dkk rates))))))
+     rates (assoc :price_eur (str (.multiply (bigdec price) (:eur rates)))
+                  :price_dkk (str (.multiply (bigdec price) (:dkk rates)))))))
 
 (def ^:private ts-fmt (DateTimeFormatter/ofPattern "dd-MM HH:mm:ss"))
 
@@ -42,11 +42,11 @@
          "<div class=\"text-center\">"
          "<p class=\"text-4xl font-bold " color "\">$" (format "%,.2f" p) "</p>"
          (when rates
-           (let [eur (double (:eur rates))
-                 dkk (double (:dkk rates))]
+           (let [p-eur (double (.multiply (bigdec price) (:eur rates)))
+                 p-dkk (double (.multiply (bigdec price) (:dkk rates)))]
              (str "<div class=\"flex justify-center gap-4 mt-3\">"
-                  "<span class=\"text-sm text-gray-600\">EUR " (format "%.4f" eur) "</span>"
-                  "<span class=\"text-sm text-gray-600\">DKK " (format "%.4f" dkk) "</span>"
+                  "<span class=\"text-sm text-gray-600\">\u20AC" (format "%,.2f" p-eur) "</span>"
+                  "<span class=\"text-sm text-gray-600\">" (format "%,.2f" p-dkk) " kr</span>"
                   "</div>")))
          "<p class=\"text-xs text-gray-400 mt-2\">Updated " ts "</p>"
          "</div></div></div>")))