Import ESP_UniClock (upstream 1189810)

Vendored from https://github.com/gpeter62/ESP_UniClock: the sketch
source, the web UI and the libraries the ESP8266 build needs, unpacked
from the bundled zips. Adds a PlatformIO project for the ESP-12. The
source is unchanged; local changes follow as separate commits.

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

firmware/uniclock/lib/ArduinoJson/extras/tests/JsonDocument/swap.cpp

@@ -0,0 +1,27 @@
+#include <ArduinoJson.h>
+
+#include <catch.hpp>
+#include <string>
+#include <utility>
+
+using namespace std;
+
+TEST_CASE("std::swap") {
+  SECTION("DynamicJsonDocument*") {
+    DynamicJsonDocument *p1, *p2;
+    swap(p1, p2);  // issue #1678
+  }
+
+  SECTION("DynamicJsonDocument") {
+    DynamicJsonDocument doc1(0x10), doc2(0x20);
+    doc1.set("hello");
+    doc2.set("world");
+
+    swap(doc1, doc2);
+
+    CHECK(doc1.capacity() == 0x20);
+    CHECK(doc1.as<string>() == "world");
+    CHECK(doc2.capacity() == 0x10);
+    CHECK(doc2.as<string>() == "hello");
+  }
+}