PTP status: 2-min average offset, details split; uptime as d/h/m/s

- Firmware: status.ptp.offset_avg_ns = mean |offset| over the last 2 min
  (one bucket per second, cleared on a clock step).
- Main panel: Time Offset (2 min avg) shows only the Bolero bracket of the
  average. Details: the current offset (coloured by the same brackets),
  hops, time/frequency traceable, version and own clock class.
- Uptime shown as "1d 2h 3m 4s".
- Preset buttons renamed: "Riedel PTP defaults", "AES67 Media PTP defaults".

Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>

components/aes67_ptp/ptp_clock.c

@@ -26,6 +26,7 @@
 #define MAX_DRIFT_PPB       500000.0
 #define WINDOW              64          // samples for interval/delay statistics
 #define SUMMARY_US          (60 * 1000000LL)
+#define AVG_S               120         // status.ptp.offset_avg_ns: mean |offset| over 2 min
 #define FLAG_PTP_TIMESCALE  0x0008      // flagField octet 1 bit 3
 #define FLAG_UNICAST        0x0400      // flagField octet 0 bit 2
 #define UTC_OFFSET          37          // TAI - UTC (s), announced as information only
@@ -102,8 +103,48 @@ static struct {
     uint32_t delay_req, delay_resp;
     uint8_t own_class;
     int64_t sum_max_ns, sum_start_us;
+    // Mean |offset| over the last AVG_S seconds (status.ptp.offset_avg_ns): one bucket per second.
+    struct {
+        int64_t sec, sum;
+        uint32_t n;
+    } avg[AVG_S];
 } s;
 
+static void avg_add(int64_t offset)
+{
+    int64_t sec = esp_timer_get_time() / 1000000;
+    typeof(s.avg[0]) *b = &s.avg[sec % AVG_S];
+    if (b->sec != sec) {
+        b->sec = sec;
+        b->sum = 0;
+        b->n = 0;
+    }
+    b->sum += llabs(offset);
+    b->n++;
+}
+
+static void avg_clear(void)
+{
+    memset(s.avg, 0, sizeof(s.avg));
+}
+
+// False while no offset was measured in the window.
+static bool avg_get(double *mean)
+{
+    int64_t now = esp_timer_get_time() / 1000000, sum = 0;
+    uint32_t n = 0;
+    for (int i = 0; i < AVG_S; i++) {
+        if (s.avg[i].n && now - s.avg[i].sec < AVG_S) {
+            sum += s.avg[i].sum;
+            n += s.avg[i].n;
+        }
+    }
+    if (n) {
+        *mean = (double)sum / n;
+    }
+    return n > 0;
+}
+
 static void win_add(window_t *w, int64_t v)
 {
     w->v[w->next] = v;
@@ -309,6 +350,7 @@ static void servo(int64_t offset)
         s.stepped = true;
         s.offset_ns = 0;    // the pre-step offset is history: not for status or the summary
         s.sum_max_ns = 0;
+        avg_clear();
         s.sum_start_us = 0;
         s.prev_t2 = 0;      // rate across the step is meaningless
         s.bad = 0;
@@ -323,6 +365,7 @@ static void servo(int64_t offset)
     s.drift_ppb = fmax(-MAX_DRIFT_PPB, fmin(MAX_DRIFT_PPB, s.drift_ppb + ki * offset));
     s.freq_ppb = -ppb;
     ptp_hw_adj_freq(s.freq_ppb);
+    avg_add(offset);
 
     if (llabs(offset) < LOCK_NS) {
         s.bad = 0;
@@ -838,6 +881,9 @@ void ptp_clock_status(cJSON *st)
         cJSON_AddBoolToObject(p, "gm_freq_traceable", s.gm.flags & 0x20);
         if (s.stepped) {
             cJSON_AddNumberToObject(p, "offset_ns", s.offset_ns);
+            if (avg_get(&mean)) {
+                cJSON_AddNumberToObject(p, "offset_avg_ns", round(mean));
+            }
             cJSON_AddNumberToObject(p, "freq_ppb", round(s.freq_ppb));
         }
         if (s.delays.n) {