Device registry (/devices + hello), static-IP fallback, WS keepalive, uncompressed fonts

- gateway: GET /devices registry (per-IP connect count, timestamps,
  device/fw from new 'hello' protocol event); graceful utterance
  errors -> error event; uvicorn ws-ping-timeout 120s
- firmware: hello on WS connect; static 192.168.86.53 fallback after
  15s without DHCP; scan-on-boot removed (kept for diagnostics);
  ping_interval 8s; fonts regenerated --no-compress (compressed
  glyphs render blank with LV_USE_FONT_COMPRESSED off); 8MB factory
  partition; montserrat_28; LVGL lock timeout semantics fixed
- docs: sauron endpoint plan, power ladder, versioning policy

Known issue: 'Outside' AP association succeeds but no L2 traffic
flows (no DHCP, no ARP) — worked once at 22:05 then never again;
ToJ side verified clean. Investigation ongoing.

Co-Authored-By: Claude Fable 5 <noreply@anthropic.com>

firmware/main/net.c

@@ -14,6 +14,36 @@
 
 static const char *TAG = "net";
 
+static esp_netif_t *s_netif;
+static volatile bool s_got_ip;
+
+/* Router DHCP has been observed to go silent for this MAC (flap throttling).
+ * After 15 s without a lease, claim the previously granted address statically. */
+static void static_ip_fallback(void *arg)
+{
+    (void)arg;
+    vTaskDelay(pdMS_TO_TICKS(15000));
+    if (!s_got_ip) {
+        ESP_LOGW(TAG, "no DHCP lease after 15s — falling back to static 192.168.86.53");
+        esp_netif_dhcpc_stop(s_netif);
+        esp_netif_ip_info_t ip = { 0 };
+        ip.ip.addr = esp_ip4addr_aton("192.168.86.53");
+        ip.gw.addr = esp_ip4addr_aton("192.168.86.1");
+        ip.netmask.addr = esp_ip4addr_aton("255.255.255.0");
+        esp_netif_set_ip_info(s_netif, &ip);
+        esp_netif_dns_info_t dns = { 0 };
+        dns.ip.u_addr.ip4.addr = esp_ip4addr_aton("192.168.86.1");
+        dns.ip.type = ESP_IPADDR_TYPE_V4;
+        esp_netif_set_dns_info(s_netif, ESP_NETIF_DNS_MAIN, &dns);
+        setenv("TZ", "CET-1CEST,M3.5.0,M10.5.0/3", 1);
+        tzset();
+        esp_sntp_config_t sntp = ESP_NETIF_SNTP_DEFAULT_CONFIG("pool.ntp.org");
+        esp_netif_sntp_init(&sntp);
+        gw_start();
+    }
+    vTaskDelete(NULL);
+}
+
 static void scan_then_connect(void *arg)
 {
     (void)arg;
@@ -38,7 +68,7 @@ static void wifi_event(void *arg, esp_event_base_t base, int32_t id, void *data)
     (void)arg;
     (void)data;
     if (base == WIFI_EVENT && id == WIFI_EVENT_STA_START) {
-        xTaskCreate(scan_then_connect, "scan", 4096, NULL, 4, NULL);
+        esp_wifi_connect();
     } else if (base == WIFI_EVENT && id == WIFI_EVENT_STA_DISCONNECTED) {
         wifi_event_sta_disconnected_t *dc = (wifi_event_sta_disconnected_t *)data;
         ESP_LOGW(TAG, "wifi disconnected (reason %d), retrying", dc ? dc->reason : -1);
@@ -47,6 +77,7 @@ static void wifi_event(void *arg, esp_event_base_t base, int32_t id, void *data)
         esp_wifi_connect();
     } else if (base == IP_EVENT && id == IP_EVENT_STA_GOT_IP) {
         ip_event_got_ip_t *ev = (ip_event_got_ip_t *)data;
+        s_got_ip = true;
         ESP_LOGI(TAG, "got ip " IPSTR, IP2STR(&ev->ip_info.ip));
         setenv("TZ", "CET-1CEST,M3.5.0,M10.5.0/3", 1);
         tzset();
@@ -65,7 +96,7 @@ void net_start(void)
     }
     ESP_ERROR_CHECK(esp_netif_init());
     ESP_ERROR_CHECK(esp_event_loop_create_default());
-    esp_netif_create_default_wifi_sta();
+    s_netif = esp_netif_create_default_wifi_sta();
 
     wifi_init_config_t cfg = WIFI_INIT_CONFIG_DEFAULT();
     ESP_ERROR_CHECK(esp_wifi_init(&cfg));
@@ -79,5 +110,6 @@ void net_start(void)
     ESP_ERROR_CHECK(esp_wifi_set_mode(WIFI_MODE_STA));
     ESP_ERROR_CHECK(esp_wifi_set_config(WIFI_IF_STA, &wc));
     ESP_ERROR_CHECK(esp_wifi_start());
+    xTaskCreate(static_ip_fallback, "ipfb", 4096, NULL, 3, NULL);
     ESP_LOGI(TAG, "wifi starting, ssid=%s", WIFI_SSID);
 }