Fix SD card integration and Lua game loading

- Fix SD card MISO pin (was using display MISO instead of SD MISO)
- Add FatFS mounting after SD card initialization
- Restore SPI baudrate on all SD init failure paths
- Add case-insensitive .lua file extension check
- Filter out hidden 8.3 filename entries
- Add SPI speed management functions for shared SPI bus
- Wrap all FatFS operations with SPI speed switching
- Restore display SPI speed (32 MHz) after SD operations
- Add debug output to Lua game loader

This fixes slow display refresh when SD card is present and enables
reliable Lua game loading from SD card /games directory.

games/lua_game.cpp

@@ -5,6 +5,7 @@
 
 #include "lua_game.h"
 #include "lua_bindings.h"
+#include "sd_card.h"
 #include <stdio.h>
 #include <string.h>
 
@@ -54,9 +55,13 @@ bool LuaGame::load_script() {
     FIL fil;
     FRESULT fr;
     
+    // Set SPI speed for SD card operations
+    uint prev_speed = sd_card_set_spi_speed();
+    
     // Open Lua script from SD card
     fr = f_open(&fil, script_path.c_str(), FA_READ);
     if (fr != FR_OK) {
+        sd_card_restore_spi_speed(prev_speed);
         error_message = "Failed to open file (FatFS error: ";
         error_message += std::to_string((int)fr);
         error_message += ")";
@@ -67,6 +72,7 @@ bool LuaGame::load_script() {
     FSIZE_t file_size = f_size(&fil);
     if (file_size == 0 || file_size > 64 * 1024) {  // Limit to 64KB
         f_close(&fil);
+        sd_card_restore_spi_speed(prev_speed);
         error_message = "Script file size invalid (0 or > 64KB)";
         return false;
     }
@@ -75,6 +81,7 @@ bool LuaGame::load_script() {
     char* script_buffer = new char[file_size + 1];
     if (!script_buffer) {
         f_close(&fil);
+        sd_card_restore_spi_speed(prev_speed);
         error_message = "Failed to allocate memory for script";
         return false;
     }
@@ -84,6 +91,9 @@ bool LuaGame::load_script() {
     fr = f_read(&fil, script_buffer, file_size, &bytes_read);
     f_close(&fil);
     
+    // Restore SPI speed immediately after file operations
+    sd_card_restore_spi_speed(prev_speed);
+    
     if (fr != FR_OK || bytes_read != file_size) {
         delete[] script_buffer;
         error_message = "Failed to read script file";

games/lua_game_loader.cpp

@@ -5,6 +5,7 @@
 
 #include "lua_game_loader.h"
 #include "lua_game.h"
+#include "sd_card.h"
 #include <stdio.h>
 #include <string.h>
 #include <vector>
@@ -51,10 +52,14 @@ bool LuaGameLoader::parse_metadata(const char* script_path, char* name, char* de
     // Default empty description
     description[0] = '\0';
     
+    // Set SPI speed for SD card operations
+    uint prev_speed = sd_card_set_spi_speed();
+    
     // Try to open file and parse metadata comments
     fr = f_open(&fil, script_path, FA_READ);
     if (fr != FR_OK) {
         printf("LuaGameLoader: Warning - could not open %s for metadata\n", script_path);
+        sd_card_restore_spi_speed(prev_speed);
         return false;
     }
     
@@ -64,6 +69,9 @@ bool LuaGameLoader::parse_metadata(const char* script_path, char* name, char* de
     fr = f_read(&fil, buffer, sizeof(buffer) - 1, &bytes_read);
     f_close(&fil);
     
+    // Restore SPI speed
+    sd_card_restore_spi_speed(prev_speed);
+    
     if (fr != FR_OK) {
         return false;
     }
@@ -109,25 +117,60 @@ int LuaGameLoader::register_all_games(GameLauncher* launcher) {
     
     printf("LuaGameLoader: Scanning /games directory for .lua scripts...\n");
     
+    // Set SPI speed for SD card operations
+    uint prev_speed = sd_card_set_spi_speed();
+    
     // Open /games directory
     fr = f_opendir(&dir, "/games");
     if (fr != FR_OK) {
         printf("LuaGameLoader: Could not open /games directory (error %d)\n", fr);
         printf("LuaGameLoader: Make sure SD card is mounted and /games exists\n");
+        sd_card_restore_spi_speed(prev_speed);
         return 0;
     }
     
     // Scan for .lua files
     while (true) {
         fr = f_readdir(&dir, &fno);
-        if (fr != FR_OK || fno.fname[0] == 0) break;  // End of directory
+        if (fr != FR_OK) {
+            printf("LuaGameLoader: Error reading directory (error %d)\n", fr);
+            break;
+        }
+        if (fno.fname[0] == 0) {
+            printf("LuaGameLoader: End of directory reached\n");
+            break;  // End of directory
+        }
+        
+        printf("LuaGameLoader: Found entry: %s (attrib=0x%02X)\n", fno.fname, fno.fattrib);
         
         // Skip directories
-        if (fno.fattrib & AM_DIR) continue;
+        if (fno.fattrib & AM_DIR) {
+            printf("LuaGameLoader:   Skipping directory\n");
+            continue;
+        }
         
-        // Check for .lua extension
+        // Skip hidden files (these are short 8.3 filename entries)
+        if (fno.fattrib & AM_HID) {
+            printf("LuaGameLoader:   Skipping hidden file (short filename entry)\n");
+            continue;
+        }
+        
+        // Check for .lua extension (case-insensitive)
         size_t len = strlen(fno.fname);
-        if (len < 5 || strcmp(fno.fname + len - 4, ".lua") != 0) continue;
+        printf("LuaGameLoader:   Filename length: %d\n", len);
+        if (len < 5) {
+            printf("LuaGameLoader:   Filename too short\n");
+            continue;
+        }
+        
+        // Case-insensitive check for .lua or .LUA
+        const char* ext = fno.fname + len - 4;
+        if (strcasecmp(ext, ".lua") != 0) {
+            printf("LuaGameLoader:   Not a .lua file (ext=%s)\n", ext);
+            continue;
+        }
+        
+        printf("LuaGameLoader:   Valid .lua file!\n");
         
         // Build full path
         char script_path[256];
@@ -160,6 +203,9 @@ int LuaGameLoader::register_all_games(GameLauncher* launcher) {
     
     f_closedir(&dir);
     
+    // Restore SPI speed
+    sd_card_restore_spi_speed(prev_speed);
+    
     printf("LuaGameLoader: Registered %d Lua games\n", count);
     return count;
 }