Add SD history UI and pin remap

- Add SD history chart + download listing to web UI
- Use HSPI for SD and fix SD pin mapping
- Swap role/OLED control pins and update role detection
- Update README pin mapping and SD/history docs

src/display_ui.cpp

@@ -69,7 +69,9 @@ void display_power_down() {
 }
 
 void display_init() {
-  pinMode(PIN_OLED_CTRL, INPUT_PULLDOWN);
+  if (g_role == DeviceRole::Sender) {
+    pinMode(PIN_OLED_CTRL, INPUT_PULLDOWN);
+  }
   Wire.begin(PIN_OLED_SDA, PIN_OLED_SCL);
   Wire.setClock(100000);
   g_display_ready = display.begin(SSD1306_SWITCHCAPVCC, OLED_I2C_ADDR);
@@ -373,7 +375,10 @@ void display_tick() {
     }
     return;
   }
-  bool ctrl_high = digitalRead(PIN_OLED_CTRL) == HIGH;
+  bool ctrl_high = false;
+  if (g_role == DeviceRole::Sender) {
+    ctrl_high = digitalRead(PIN_OLED_CTRL) == HIGH;
+  }
 
   bool in_boot_window = (millis() - g_boot_ms) < OLED_AUTO_OFF_MS;
   if (g_role == DeviceRole::Receiver) {