Initial commit: standalone Pyxis T-Deck firmware

Split T-Deck firmware from microReticulum examples/lxmf_tdeck/ into its
own repo. microReticulum is consumed as a git submodule dependency pinned
to feat/t-deck. All include paths updated from relative symlinks to bare
includes resolved via library build flags.

Both tdeck (NimBLE) and tdeck-bluedroid environments compile successfully.
Licensed under AGPLv3.

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

lib/tdeck_ui/UI/Clipboard.cpp

@@ -0,0 +1,8 @@
+#include "Clipboard.h"
+
+namespace UI {
+
+String Clipboard::_content = "";
+bool Clipboard::_has_content = false;
+
+}  // namespace UI