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/containsKey.cpp

@@ -0,0 +1,44 @@
+// ArduinoJson - https://arduinojson.org
+// Copyright © 2014-2022, Benoit BLANCHON
+// MIT License
+
+#include <ArduinoJson.h>
+#include <catch.hpp>
+
+TEST_CASE("JsonDocument::containsKey()") {
+  DynamicJsonDocument doc(4096);
+
+  SECTION("returns true on object") {
+    doc["hello"] = "world";
+
+    REQUIRE(doc.containsKey("hello") == true);
+  }
+
+  SECTION("returns true when value is null") {
+    doc["hello"] = static_cast<const char*>(0);
+
+    REQUIRE(doc.containsKey("hello") == true);
+  }
+
+  SECTION("returns true when key is a std::string") {
+    doc["hello"] = "world";
+
+    REQUIRE(doc.containsKey(std::string("hello")) == true);
+  }
+
+  SECTION("returns false  on object") {
+    doc["world"] = "hello";
+
+    REQUIRE(doc.containsKey("hello") == false);
+  }
+
+  SECTION("returns false on array") {
+    doc.add("hello");
+
+    REQUIRE(doc.containsKey("hello") == false);
+  }
+
+  SECTION("returns false on null") {
+    REQUIRE(doc.containsKey("hello") == false);
+  }
+}