feat(firmware): enable task watchdog on camera/reporter/loop tasks

30s TWDT subscribes all three long-running tasks and panics on hang.
The reporter task's retry loop explicitly feeds between attempts so
the 3-try sequence (worst case 52s) does not itself trip the dog.
Reset reason on next boot is visible via esp_reset_reason() which
EVT_BOOT already logs.

firmware/src/main.cpp

@@ -11,6 +11,7 @@
 #include "event_log.h"
 #include "net_guard.h"
 #include <esp_system.h>
+#include <esp_task_wdt.h>
 
 // LED on GPIO2 (TimerCamera-F built-in LED) — verify against board schematic
 // Factory reset: hold GPIO37 (BOOT button) for 5 seconds
@@ -53,6 +54,7 @@ static void check_factory_reset() {
             ESP.restart();
         }
         delay(50);
+        esp_task_wdt_reset();
     }
 }
 
@@ -60,6 +62,7 @@ static void check_factory_reset() {
 static void task_camera(void*) {
     static uint8_t frame[CV_PIXELS];  // static: avoids 9KB on task stack
     int last_logged_track_id = 0;     // diagnostic: log each new track once
+    esp_task_wdt_add(nullptr);
     while (true) {
         if (camera_capture_96(frame)) {
             if (xSemaphoreTake(s_cv_mutex, pdMS_TO_TICKS(100)) == pdTRUE) {
@@ -86,15 +89,18 @@ static void task_camera(void*) {
             }
         }
         vTaskDelay(pdMS_TO_TICKS(CAM_INTERVAL_MS));
+        esp_task_wdt_reset();
     }
 }
 
 // Hourly reporter task — runs on core 0
 static void task_reporter(void*) {
     uint32_t last_report_ts = 0; // 0 = not initialized yet
+    esp_task_wdt_add(nullptr);
 
     while (true) {
         vTaskDelay(pdMS_TO_TICKS(10000)); // check every 10s
+        esp_task_wdt_reset();
 
         uint32_t now = (uint32_t)(time(nullptr));
         if (now < 1700000000UL) continue; // NTP not synced
@@ -203,11 +209,17 @@ void setup() {
 
     s_cv_mutex = xSemaphoreCreateMutex();
 
+    // Task watchdog: 30s timeout, panic on trigger so we reboot and log
+    // via esp_reset_reason() in EVT_BOOT on the next boot.
+    esp_task_wdt_init(30, /*panic=*/true);
+    esp_task_wdt_add(nullptr); // subscribe the Arduino loopTask
+
     xTaskCreatePinnedToCore(task_camera,   "cam",  8192, nullptr, 2, nullptr, 1);
     xTaskCreatePinnedToCore(task_reporter, "rep",  8192, nullptr, 1, nullptr, 0);
 }
 
 void loop() {
+    esp_task_wdt_reset();
     ArduinoOTA.handle();
     check_factory_reset();
     net_guard_tick();

firmware/src/reporter.cpp

@@ -8,6 +8,7 @@
 #include <vector>
 #include <time.h>
 #include <freertos/semphr.h>
+#include <esp_task_wdt.h>
 
 static std::vector<CameraHourlyRecord> s_cam_buf;
 static std::vector<BLEHourlyRecord>    s_ble_buf;
@@ -53,12 +54,14 @@ static bool post_json_once(const DeviceConfig& cfg, const char* path, const Stri
 }
 
 static bool post_json(const DeviceConfig& cfg, const char* path, const String& body) {
-    // 3 attempts with 0/2s/5s delays. Total worst case ~ 2x(5+10)s + 7s = 37s;
-    // acceptable for an hourly task and within the 30s TWDT once Task 6 lands
-    // IF TWDT is fed between attempts (see Task 6).
+    // 3 attempts. Worst case per call: 3 × (5s connect + 10s response) + 0 + 2 + 5 = 52s.
+    // TWDT is fed before the backoff delay and before each attempt so the 30s
+    // timeout doesn't fire mid-sequence.
     static const uint16_t DELAYS_MS[] = { 0, 2000, 5000 };
     for (int i = 0; i < 3; i++) {
+        esp_task_wdt_reset();
         if (DELAYS_MS[i]) vTaskDelay(pdMS_TO_TICKS(DELAYS_MS[i]));
+        esp_task_wdt_reset();
         if (post_json_once(cfg, path, body)) return true;
     }
     return false;