fix(lite): name the cause when the backend isn't linked

A lite build compiled without the SDXL backend (DRAGONX_ENABLE_LITE_BACKEND off,
i.e. built with --lite instead of --lite-backend) leaves the controller null, so
the wallet never opens and the UI shows a silent "disconnected" state. The Console
status now states the cause and the fix directly ("Lite backend not linked in this
build (rebuild with --lite-backend)") instead of a vague "unavailable".

Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>

src/ui/windows/lite_console_tab.cpp

@@ -62,7 +62,10 @@ void RenderLiteConsoleTab(App* app)
         const char* connText;
         ImU32 connCol;
         if (!lw) {
-            connText = "Lite backend unavailable";
+            // lite_wallet_ is null only when DRAGONX_ENABLE_LITE_BACKEND is off, i.e. the build
+            // was compiled without the SDXL backend. This can only appear in a misconfigured
+            // build, so name the fix directly.
+            connText = "Lite backend not linked in this build (rebuild with --lite-backend)";
             connCol = Error();
         } else if (lw->walletOpen()) {
             connText = "Connected";