feat: establish the bounded production architecture

include/diagnostics.h

@@ -0,0 +1,13 @@
+#pragma once
+
+#include <stdint.h>
+
+typedef struct {
+  uint64_t uptime_ms;
+  uint32_t free_heap_bytes;
+  uint32_t minimum_free_heap_bytes;
+  uint32_t largest_free_block_bytes;
+  uint16_t connected_clients;
+  uint16_t rejected_oversized_input;
+  int reset_reason;
+} diagnostics_t;