merge: upstream/dev into webconfig (v1.16.0 base -> 2026-07-19)

First upstream merge since the 2026-06-06 base (191 upstream commits). 14 files
conflicted; resolutions below.

Fleet-critical check (Constraint 1): upstream reordered NodePrefs members
(rx_boosted_gain / path_hash_mode moved to the struct tail) but did NOT change
/com_prefs. Persistence is written field-by-field at explicit offsets, so member
order is in-memory only. Verified the fork's writeCommonPrefsImage() is
byte-identical to upstream's inline writer at every offset (79 pad, 121, 122,
290-294). No migration needed.

Resolutions:
- CommonCLI.h: kept the fork's NodePrefs (superset) and adopted upstream's
  setRxBoostedGain(bool)->bool signature change, which CommonCLI.cpp now uses to
  report unsupported. Corrected a stale comment claiming rx_boosted_gain lives at
  offset 79 (it is a pad; the field is at 290).
- CommonCLI.cpp: kept the fork's legacy /com_prefs migration and the extracted
  writeCommonPrefsImage() call.
- UITask.cpp: three-way merge - upstream's drawTextCentered + powering-off
  screen, plus the fork's WITH_WEBCONFIG portal/reboot screens.
- ESP32Board.cpp, MeshCore.h, platformio.ini: kept both sides (fork OTA additions
  alongside upstream powerOff/enterDeepSleep and Packet.cpp).
- MicroNMEALocationProvider.h: took upstream's claim/release and added the
  _claims member they depend on.
- MyMesh.cpp/.h (repeater + room server): kept the fork's superset defaults.
- Removed duplicate declarations auto-merge produced: RadioLibWrapper::_cad_enabled
  and MyMesh::getCADEnabled().

Verification: native suite 15/15 (incl. upstream's new test_mesh_tables), both
MQTT smoke builds green, ArduinoJson pin check passes. Hardware validation next.

examples/simple_secure_chat/main.cpp

@@ -135,7 +135,7 @@ class MyMesh : public BaseChatMesh, ContactVisitor {
     File file = _fs->open("/contacts", "w", true);
 #endif
     if (file) {
-      ContactsIterator iter;
+      ContactsIterator iter = startContactsIterator();
       ContactInfo c;
       uint8_t unused = 0;
       uint32_t reserved = 0;
@@ -560,6 +560,10 @@ void setup() {
 
   board.begin();
 
+#ifdef HAS_EXTERNAL_WATCHDOG
+  external_watchdog.begin();
+#endif
+
   if (!radio_init()) { halt(); }
 
   fast_rng.begin(radio_driver.getRngSeed());
@@ -591,4 +595,7 @@ void setup() {
 void loop() {
   the_mesh.loop();
   rtc_clock.tick();
+#ifdef HAS_EXTERNAL_WATCHDOG
+  external_watchdog.loop();
+#endif
 }