Merge upstream dev through 428a95c64

Integrate fractional Companion timezones and conditional Bluetooth pages while preserving the existing preference byte layout, transactional saves, and Full transport selector. Add migration, rollback, invalid-value, and UI profile regressions.

src/helpers/CompanionTimezonePrefs.h

@@ -0,0 +1,46 @@
+#pragma once
+
+#include "CompanionTrafficPrefs.h"
+#include <stdint.h>
+#include <string.h>
+
+namespace mesh { namespace companion { namespace timezone {
+
+// Optional footer after all existing preference fields and PMO/TXR footers.
+// Integer-only images retain their exact published bytes and lengths.
+static constexpr size_t FooterSize = 10;
+
+inline bool valid(float hours) {
+  // Ordered comparisons also reject NaN and either infinity.
+  return hours >= -12.0f && hours <= 14.0f;
+}
+
+inline bool fractional(float hours) {
+  return valid(hours) && hours != static_cast<int8_t>(hours);
+}
+
+inline void encodeFooter(uint8_t out[FooterSize], float hours) {
+  static_assert(sizeof(float) == sizeof(uint32_t), "32-bit timezone float");
+  out[0] = 'T'; out[1] = 'Z'; out[2] = 'F'; out[3] = 1;
+  uint32_t bits;
+  memcpy(&bits, &hours, sizeof(bits));
+  for (unsigned i = 0; i < 4; ++i) out[4 + i] = uint8_t(bits >> (8 * i));
+  const uint16_t crc = traffic::checksum(out, 8);
+  out[8] = uint8_t(crc >> 8); out[9] = uint8_t(crc);
+}
+
+inline bool decodeFooter(const uint8_t* in, size_t size, float& hours) {
+  if (!in || size != FooterSize || in[0] != 'T' || in[1] != 'Z'
+      || in[2] != 'F' || in[3] != 1
+      || traffic::checksum(in, 8) != uint16_t((in[8] << 8) | in[9]))
+    return false;
+  uint32_t bits = 0;
+  for (unsigned i = 0; i < 4; ++i) bits |= uint32_t(in[4 + i]) << (8 * i);
+  float decoded;
+  memcpy(&decoded, &bits, sizeof(decoded));
+  if (!valid(decoded)) return false;
+  hours = decoded;
+  return true;
+}
+
+} } }  // namespace mesh::companion::timezone