feat(display): add R8 portrait observer layouts

src/helpers/ui/DisplayFrameSignature.h

@@ -0,0 +1,23 @@
+#pragma once
+
+#include <stdint.h>
+
+namespace DisplayFrameSignature {
+
+static constexpr uint32_t INITIAL = 2166136261u;
+
+inline uint32_t append(uint32_t signature, const char *text) {
+  if (text) {
+    while (*text) {
+      signature ^= static_cast<uint8_t>(*text++);
+      signature *= 16777619u;
+    }
+  }
+
+  // Separate adjacent fields so { "ab", "c" } differs from { "a", "bc" }.
+  signature ^= 0xFFu;
+  signature *= 16777619u;
+  return signature;
+}
+
+} // namespace DisplayFrameSignature