encoding fix

include/text_utils.h

@@ -0,0 +1,35 @@
+#pragma once
+#include <Arduino.h>
+
+// The M5Stack default font does not correctly render UTF-8 encoded German
+// umlauts (ä, ö, ü, ß), they show up as garbled characters or boxes.
+// This helper replaces them with their common ASCII transliteration
+// (ö -> oe, ä -> ae, ü -> ue, ß -> ss) before printing to the display.
+// This is the simplest, most robust fix without needing a custom font.
+inline String sanitizeGermanText(const String &input) {
+    String out;
+    out.reserve(input.length());
+
+    for (size_t i = 0; i < input.length(); i++) {
+        unsigned char c1 = input[i];
+
+        // UTF-8 two-byte sequences for German umlauts start with 0xC3
+        if (c1 == 0xC3 && i + 1 < input.length()) {
+            unsigned char c2 = input[i + 1];
+            switch (c2) {
+                case 0xA4: out += "ae"; i++; continue; // ä
+                case 0xB6: out += "oe"; i++; continue; // ö
+                case 0xBC: out += "ue"; i++; continue; // ü
+                case 0x84: out += "Ae"; i++; continue; // Ä
+                case 0x96: out += "Oe"; i++; continue; // Ö
+                case 0x9C: out += "Ue"; i++; continue; // Ü
+                case 0x9F: out += "ss"; i++; continue; // ß
+                default: break;
+            }
+        }
+
+        out += (char)c1;
+    }
+
+    return out;
+}