feat(LuaGame): migrate solitaire, enable SD external loading

- Enable use_external=true with priority: solitaire, breakout, game, pong, snake, tetris
- Fix is_pico detection to check source content before load (renderer./INPUT.) instead of game.vars heuristic that always true
- Successfully uploaded solitaire.lua (24824 bytes) via /fs/upload?path=/sdcard/lua/solitaire.lua
- Tested solitaire loads: 'loaded external /sdcard/lua/solitaire.lua 24824 bytes, pico=1, FPS 13.0'
- Screenshot shows card layout rendering (white pixels 4141, ASCII preview shows piles)
- SD file listing: /sdcard/lua now has breakout.lua and solitaire.lua
- Ready for further pico games via same upload API

Apps/LuaGame/main/Source/main.c

@@ -452,18 +452,22 @@ static void lua_init_task(void* arg){
     luaL_openlibs(ctx->L);
     register_sys(ctx->L);
     const char* external_paths[]={
+        "/sdcard/lua/solitaire.lua",
         "/sdcard/lua/breakout.lua",
         "/sdcard/lua/game.lua",
+        "/sdcard/lua/pong.lua",
+        "/sdcard/lua/snake.lua",
+        "/sdcard/lua/tetris.lua",
         NULL
     };
     char* src_buf=NULL;
     size_t src_len=0;
     const char* loaded_from="embedded";
-    bool use_external = false;
-    bool use_pico_test = false; // set true to test pico games
+    bool use_external = true; // enable SD loading for solitaire migration
+    bool use_pico_test = false;
     const char* pico_test_src = NULL;
     if(use_pico_test){
-        pico_test_src = pong_lua_src; // choose pong for test
+        pico_test_src = pong_lua_src;
         printf("[LuaGame] using Pico test game: Pong (%d bytes)\n", (int)strlen(pico_test_src));
         src_len = strlen(pico_test_src);
         src_buf = (char*)alloc_psram(src_len+1);