fix(stability): disable dangerous mbedtls free configs, place panic handler in IRAM, and make prefetch safe and on-demand

main/Kconfig.projbuild

@@ -10,7 +10,7 @@ menu "MTG RFID Companion"
 
     config MTG_SCAN_PREFETCH
         bool "Prefetch card data for all mapped UIDs at boot"
-        default y
+        default n
 
     config MTG_GITEA_URL
         string "Gitea instance base URL (e.g. https://gitea.com)"

main/scryfall_client.c

@@ -87,6 +87,7 @@ typedef struct {
     size_t cap;
     esp_err_t err;
     FILE *file;   /* when downloading to a file */
+    const char *file_path;
     int status;
 } http_sink_t;
 
@@ -153,11 +154,22 @@ static esp_err_t http_request(const char *url, http_sink_t *sink)
         return ESP_ERR_TIMEOUT;
     }
 
+    /* Disable power save during HTTPS requests for maximum reliability */
+    wifi_manager_set_power_save(false);
+
     esp_err_t overall_ret = ESP_FAIL;
     for (int attempt = 0; attempt < MAX_ATTEMPTS; attempt++) {
         if (sink->file != NULL) {
-            rewind(sink->file);
-            ftruncate(fileno(sink->file), 0);
+            if (attempt > 0 && sink->file_path != NULL) {
+                fclose(sink->file);
+                sink->file = fopen(sink->file_path, "wb");
+                if (sink->file == NULL) {
+                    overall_ret = ESP_FAIL;
+                    break;
+                }
+            } else {
+                rewind(sink->file);
+            }
         } else {
             sink->len = 0;
         }
@@ -171,6 +183,7 @@ static esp_err_t http_request(const char *url, http_sink_t *sink)
             .user_data = sink,
             .buffer_size = 2048,
             .crt_bundle_attach = esp_crt_bundle_attach,
+            .keep_alive_enable = false,
         };
         esp_http_client_handle_t client = esp_http_client_init(&cfg);
         if (client == NULL) {
@@ -201,6 +214,7 @@ static esp_err_t http_request(const char *url, http_sink_t *sink)
         vTaskDelay(pdMS_TO_TICKS(500));
     }
 
+    wifi_manager_set_power_save(true);
     wifi_manager_release_net_lock();
     return overall_ret;
 }
@@ -230,7 +244,7 @@ static esp_err_t http_download_file(const char *url, const char *path)
     if (f == NULL) {
         return ESP_FAIL;
     }
-    http_sink_t sink = { .file = f };
+    http_sink_t sink = { .file = f, .file_path = tmp };
     esp_err_t ret = http_request(url, &sink);
     fclose(f);
     if (ret != ESP_OK) {
@@ -441,8 +455,17 @@ static esp_err_t scryfall_ensure_cached(const char *card_name, const char *uid)
 /*  net_task                                                           */
 /* ------------------------------------------------------------------ */
 
+#ifdef CONFIG_MTG_SCAN_PREFETCH
 static void prefetch_mappings(void)
 {
+    /* Settle delay: give system and Wi-Fi time to settle before background fetch */
+    vTaskDelay(pdMS_TO_TICKS(5000));
+
+    if (esp_get_free_heap_size() < 40000) {
+        ESP_LOGW(TAG, "Heap too low (%u bytes) for startup prefetch, skipping", (unsigned int)esp_get_free_heap_size());
+        return;
+    }
+
     char *buf = NULL;
     size_t len = 0;
     if (storage_read_text(STORAGE_MAPPINGS, &buf, &len) != ESP_OK || buf == NULL) {
@@ -463,12 +486,14 @@ static void prefetch_mappings(void)
     cJSON_ArrayForEach(item, root) {
         uid = item->string;
         if (uid == NULL || item->valuestring == NULL) continue;
-        scryfall_ensure_cached(item->valuestring, uid);
+        /* Call scryfall_do_fetch directly so we do not clobber UI fetch signaling */
+        scryfall_do_fetch(item->valuestring, uid);
         /* Rate-limit delay: Scryfall requests 50-100ms between queries */
-        vTaskDelay(pdMS_TO_TICKS(100));
+        vTaskDelay(pdMS_TO_TICKS(150));
     }
     cJSON_Delete(root);
 }
+#endif
 
 static void net_task(void *arg)
 {