feat: Add ALERT command for temp/heap threshold monitoring

ALERT TEMP <celsius> and ALERT HEAP <bytes> emit EVENT packets
when thresholds are crossed (60s holdoff). NVS-persisted, shown
in STATUS and CONFIG. Temp alerts require SOC_TEMP_SENSOR_SUPPORTED.

get-started/csi_recv_router/main/app_main.c

@@ -211,6 +211,15 @@ static int64_t  s_chanscan_last = 0;
 #define PROBE_DEDUP_DEFAULT_US  10000000LL
 static int64_t s_probe_dedup_us = PROBE_DEDUP_DEFAULT_US;
 
+/* Alert thresholds (0 = disabled) */
+#define ALERT_HOLDOFF_US  60000000LL  /* 60s debounce between alerts */
+static float    s_alert_temp_thresh = 0.0f;  /* celsius, e.g. 70.0 */
+static uint32_t s_alert_heap_thresh = 0;     /* bytes, e.g. 30000 */
+#if SOC_TEMP_SENSOR_SUPPORTED
+static int64_t  s_alert_temp_last = 0;
+#endif
+static int64_t  s_alert_heap_last = 0;
+
 /* --- NVS helpers --- */
 
 static void config_load_nvs(void)
@@ -313,11 +322,20 @@ static void config_load_nvs(void)
         if (nvs_get_i8(h, "csi_enabled", &csi_en) == ESP_OK) {
             s_csi_enabled = (csi_en != 0);
         }
+        int32_t alert_temp;
+        if (nvs_get_i32(h, "alert_temp", &alert_temp) == ESP_OK && alert_temp > 0) {
+            s_alert_temp_thresh = (float)alert_temp / 10.0f;  /* stored as 10ths of degree */
+        }
+        int32_t alert_heap;
+        if (nvs_get_i32(h, "alert_heap", &alert_heap) == ESP_OK && alert_heap > 0) {
+            s_alert_heap_thresh = (uint32_t)alert_heap;
+        }
         nvs_close(h);
-        ESP_LOGI(TAG, "NVS loaded: hostname=%s rate=%d tx_power=%d adaptive=%d threshold=%.6f ble=%d target=%s:%d csi_mode=%d hybrid_n=%d powersave=%d presence=%d pr_thresh=%.4f baseline_nsub=%d led_quiet=%d csi=%d",
+        ESP_LOGI(TAG, "NVS loaded: hostname=%s rate=%d tx_power=%d adaptive=%d threshold=%.6f ble=%d target=%s:%d csi_mode=%d hybrid_n=%d powersave=%d presence=%d pr_thresh=%.4f baseline_nsub=%d led_quiet=%d csi=%d alert_temp=%.1f alert_heap=%lu",
                  s_hostname, s_send_frequency, s_tx_power_dbm, s_adaptive, s_motion_threshold, s_ble_enabled,
                  s_target_ip, s_target_port, (int)s_csi_mode, s_hybrid_interval, s_powersave,
-                 s_presence_enabled, s_pr_threshold, s_baseline_nsub, s_led_quiet, s_csi_enabled);
+                 s_presence_enabled, s_pr_threshold, s_baseline_nsub, s_led_quiet, s_csi_enabled,
+                 s_alert_temp_thresh, (unsigned long)s_alert_heap_thresh);
     } else {
         ESP_LOGI(TAG, "NVS: no saved config, using defaults");
     }
@@ -992,6 +1010,53 @@ static void adaptive_task(void *arg)
             }
         }
 
+        /* Alert threshold checks */
+        {
+            int64_t now_alert = esp_timer_get_time();
+
+            /* Heap alert */
+            if (s_alert_heap_thresh > 0) {
+                uint32_t free_heap = esp_get_free_heap_size();
+                if (free_heap < s_alert_heap_thresh &&
+                    (now_alert - s_alert_heap_last) > ALERT_HOLDOFF_US) {
+                    s_alert_heap_last = now_alert;
+                    char event[128];
+                    int len = snprintf(event, sizeof(event),
+                        "EVENT,%s,alert=heap free=%lu thresh=%lu",
+                        s_hostname, (unsigned long)free_heap,
+                        (unsigned long)s_alert_heap_thresh);
+                    if (s_udp_socket >= 0) {
+                        sendto(s_udp_socket, event, len, 0,
+                            (struct sockaddr *)&s_dest_addr, sizeof(s_dest_addr));
+                    }
+                    ESP_LOGW(TAG, "ALERT: heap low (%lu < %lu)",
+                             (unsigned long)free_heap, (unsigned long)s_alert_heap_thresh);
+                }
+            }
+
+            /* Temperature alert */
+#if SOC_TEMP_SENSOR_SUPPORTED
+            if (s_alert_temp_thresh > 0.0f && s_temp_handle) {
+                float temp = 0.0f;
+                if (temperature_sensor_get_celsius(s_temp_handle, &temp) == ESP_OK &&
+                    temp > s_alert_temp_thresh &&
+                    (now_alert - s_alert_temp_last) > ALERT_HOLDOFF_US) {
+                    s_alert_temp_last = now_alert;
+                    char event[128];
+                    int len = snprintf(event, sizeof(event),
+                        "EVENT,%s,alert=temp value=%.1f thresh=%.1f",
+                        s_hostname, temp, s_alert_temp_thresh);
+                    if (s_udp_socket >= 0) {
+                        sendto(s_udp_socket, event, len, 0,
+                            (struct sockaddr *)&s_dest_addr, sizeof(s_dest_addr));
+                    }
+                    ESP_LOGW(TAG, "ALERT: temp high (%.1f > %.1f)",
+                             temp, s_alert_temp_thresh);
+                }
+            }
+#endif
+        }
+
         if (!s_adaptive || s_energy_idx < WANDER_WINDOW) continue;
 
         /* Compute mean */
@@ -1602,6 +1667,7 @@ static int cmd_handle(const char *cmd, char *reply, size_t reply_size)
                  " temp=%.1f csi_count=%lu boots=%lu rssi_min=%d rssi_max=%d"
                  " csi=%s csi_mode=%s hybrid_n=%d auth=%s flood_thresh=%d/%d powersave=%s"
                  " presence=%s pr_score=%.4f chanscan=%s led=%s"
+                 " alert_temp=%.1f alert_heap=%lu"
                  " nvs_used=%lu nvs_free=%lu nvs_total=%lu part_size=%lu"
                  " built=%s_%s idf=%s chip=%sr%dc%d",
                  uptime_str, (long long)up, (unsigned long)heap, rssi, channel, (int)s_tx_power_dbm,
@@ -1617,6 +1683,7 @@ static int cmd_handle(const char *cmd, char *reply, size_t reply_size)
                  s_powersave ? "on" : "off",
                  s_presence_enabled ? "on" : "off", s_pr_last_score,
                  s_chanscan_enabled ? "on" : "off", s_led_quiet ? "quiet" : "auto",
+                 s_alert_temp_thresh, (unsigned long)s_alert_heap_thresh,
                  (unsigned long)nvs_stats.used_entries,
                  (unsigned long)nvs_stats.free_entries,
                  (unsigned long)nvs_stats.total_entries,
@@ -2194,6 +2261,48 @@ static int cmd_handle(const char *cmd, char *reply, size_t reply_size)
         return strlen(reply);
     }
 
+    /* ALERT — set temp/heap alert thresholds */
+    if (strcmp(cmd, "ALERT") == 0) {
+        snprintf(reply, reply_size, "OK ALERT temp=%.1f heap=%lu (0=off)",
+                 s_alert_temp_thresh, (unsigned long)s_alert_heap_thresh);
+        return strlen(reply);
+    }
+    if (strncmp(cmd, "ALERT ", 6) == 0) {
+        const char *arg = cmd + 6;
+        if (strncmp(arg, "TEMP ", 5) == 0) {
+            float val = strtof(arg + 5, NULL);
+            if (val < 0 || val > 125) {
+                snprintf(reply, reply_size, "ERR ALERT TEMP range 0-125 (0=off)");
+                return strlen(reply);
+            }
+            s_alert_temp_thresh = val;
+            config_save_i32("alert_temp", (int32_t)(val * 10.0f));
+            snprintf(reply, reply_size, "OK ALERT TEMP %.1f", val);
+            return strlen(reply);
+        }
+        if (strncmp(arg, "HEAP ", 5) == 0) {
+            int val = atoi(arg + 5);
+            if (val < 0 || val > 300000) {
+                snprintf(reply, reply_size, "ERR ALERT HEAP range 0-300000 (0=off)");
+                return strlen(reply);
+            }
+            s_alert_heap_thresh = (uint32_t)val;
+            config_save_i32("alert_heap", val);
+            snprintf(reply, reply_size, "OK ALERT HEAP %d", val);
+            return strlen(reply);
+        }
+        if (strcmp(arg, "OFF") == 0) {
+            s_alert_temp_thresh = 0.0f;
+            s_alert_heap_thresh = 0;
+            config_save_i32("alert_temp", 0);
+            config_save_i32("alert_heap", 0);
+            snprintf(reply, reply_size, "OK ALERT all disabled");
+            return strlen(reply);
+        }
+        snprintf(reply, reply_size, "ERR ALERT TEMP <c>|HEAP <bytes>|OFF");
+        return strlen(reply);
+    }
+
     /* HELP */
     if (strcmp(cmd, "HELP") == 0) {
         int pos = 0;
@@ -2207,7 +2316,7 @@ static int cmd_handle(const char *cmd, char *reply, size_t reply_size)
             "CALIBRATE [STATUS|CLEAR|N]  PRESENCE [ON|OFF|THRESHOLD]\n"
             "CHANSCAN [ON|OFF|NOW|INTERVAL]  LED [QUIET|AUTO]\n"
             "POWERSAVE [ON|OFF]  AUTH [secret|OFF]  FLOODTHRESH <n> [win]\n"
-            "LOG <NONE|ERROR|WARN|INFO|DEBUG|VERBOSE>  RSSI RESET\n"
+            "ALERT [TEMP <c>|HEAP <bytes>|OFF]  LOG <level>  RSSI RESET\n"
             "OTA <url>  POWERTEST [dwell]  IDENTIFY  REBOOT  FACTORY");
         return pos;
     }
@@ -2254,6 +2363,8 @@ static int cmd_handle(const char *cmd, char *reply, size_t reply_size)
             "powersave=%s\n"
             "auth=%s\n"
             "flood_thresh=%d/%ds\n"
+            "alert_temp=%.1f\n"
+            "alert_heap=%lu\n"
             "boots=%lu",
             s_hostname,
             s_send_frequency,
@@ -2276,6 +2387,7 @@ static int cmd_handle(const char *cmd, char *reply, size_t reply_size)
             s_powersave ? "on" : "off",
             s_auth_secret[0] ? "on" : "off",
             s_flood_thresh, s_flood_window_s,
+            s_alert_temp_thresh, (unsigned long)s_alert_heap_thresh,
             (unsigned long)s_boot_count);
         return pos;
     }