refactor: Zeitraum-Dropdown in DetailModal auf Listbox mit Littwin-Design umgestellt

- <select> durch Headless UI Listbox ersetzt
- Optionen DIA0, DIA1, DIA2 mit deutschem Label dargestellt
- Einheitliches Styling mit littwin-blue wie in anderen Komponenten

components/main/system/DetailModal.tsx

@@ -4,6 +4,7 @@ import React from "react";
 import { Line } from "react-chartjs-2";
 import { useSelector } from "react-redux";
 import { RootState } from "@/redux/store";
+import { Listbox } from "@headlessui/react";
 
 type Props = {
   isOpen: boolean;
@@ -78,19 +79,59 @@ export const DetailModal = ({
           </button>
         </div>
 
-        <div className="mb-4">
-          <label className="mr-2 font-medium">Zeitraum:</label>
-          <select
-            className="border px-2 py-1 rounded"
-            value={zeitraum}
-            onChange={(e) =>
-              setZeitraum(e.target.value as "DIA0" | "DIA1" | "DIA2")
-            }
-          >
-            <option value="DIA0">Alle Messwerte</option>
-            <option value="DIA1">Stündlich</option>
-            <option value="DIA2">Täglich</option>
-          </select>
+        <div className="flex items-center space-x-2 mb-4">
+          <label className="font-medium">Zeitraum:</label>
+          <Listbox value={zeitraum} onChange={setZeitraum}>
+            <div className="relative w-48">
+              <Listbox.Button className="w-full border px-3 py-1 rounded text-left bg-white flex justify-between items-center text-sm">
+                <span>
+                  {
+                    {
+                      DIA0: "Alle Messwerte",
+                      DIA1: "Stündlich",
+                      DIA2: "Täglich",
+                    }[zeitraum]
+                  }
+                </span>
+                <svg
+                  className="w-5 h-5 text-gray-400"
+                  viewBox="0 0 20 20"
+                  fill="currentColor"
+                >
+                  <path
+                    fillRule="evenodd"
+                    d="M5.23 7.21a.75.75 0 011.06.02L10 10.585l3.71-3.355a.75.75 0 111.02 1.1l-4.25 3.85a.75.75 0 01-1.02 0l-4.25-3.85a.75.75 0 01.02-1.06z"
+                    clipRule="evenodd"
+                  />
+                </svg>
+              </Listbox.Button>
+              <Listbox.Options className="absolute z-50 mt-1 w-full border rounded bg-white shadow max-h-60 overflow-auto text-sm">
+                {["DIA0", "DIA1", "DIA2"].map((option) => (
+                  <Listbox.Option
+                    key={option}
+                    value={option}
+                    className={({ selected, active }) =>
+                      `px-4 py-1 cursor-pointer ${
+                        selected
+                          ? "bg-littwin-blue text-white"
+                          : active
+                          ? "bg-blue-100"
+                          : ""
+                      }`
+                    }
+                  >
+                    {
+                      {
+                        DIA0: "Alle Messwerte",
+                        DIA1: "Stündlich",
+                        DIA2: "Täglich",
+                      }[option]
+                    }
+                  </Listbox.Option>
+                ))}
+              </Listbox.Options>
+            </div>
+          </Listbox>
         </div>
 
         <div className="h-[85%]">