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/config.cpp

@@ -2,5 +2,5 @@
 
 DeviceRole detect_role() {
   pinMode(PIN_ROLE, INPUT_PULLDOWN);
-  return digitalRead(PIN_ROLE) == HIGH ? DeviceRole::Receiver : DeviceRole::Sender;
+  return digitalRead(PIN_ROLE) == HIGH ? DeviceRole::Sender : DeviceRole::Receiver;
 }