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/JsonSerializer/std_stream.cpp

@@ -0,0 +1,66 @@
+// ArduinoJson - https://arduinojson.org
+// Copyright © 2014-2022, Benoit BLANCHON
+// MIT License
+
+#include <ArduinoJson.h>
+#include <catch.hpp>
+#include <sstream>
+
+TEST_CASE("operator<<(std::ostream)") {
+  DynamicJsonDocument doc(4096);
+  std::ostringstream os;
+
+  SECTION("JsonVariant containing false") {
+    JsonVariant variant = doc.to<JsonVariant>();
+
+    variant.set(false);
+    os << variant;
+
+    REQUIRE("false" == os.str());
+  }
+
+  SECTION("JsonVariant containing string") {
+    JsonVariant variant = doc.to<JsonVariant>();
+
+    variant.set("coucou");
+    os << variant;
+
+    REQUIRE("\"coucou\"" == os.str());
+  }
+
+  SECTION("JsonObject") {
+    JsonObject object = doc.to<JsonObject>();
+    object["key"] = "value";
+
+    os << object;
+
+    REQUIRE("{\"key\":\"value\"}" == os.str());
+  }
+
+  SECTION("MemberProxy") {
+    JsonObject object = doc.to<JsonObject>();
+    object["key"] = "value";
+
+    os << object["key"];
+
+    REQUIRE("\"value\"" == os.str());
+  }
+
+  SECTION("JsonArray") {
+    JsonArray array = doc.to<JsonArray>();
+    array.add("value");
+
+    os << array;
+
+    REQUIRE("[\"value\"]" == os.str());
+  }
+
+  SECTION("ElementProxy") {
+    JsonArray array = doc.to<JsonArray>();
+    array.add("value");
+
+    os << array[0];
+
+    REQUIRE("\"value\"" == os.str());
+  }
+}