feat: orientation model, password confirm, frontend build

- Collapse orientation to landscape/portrait (ribbon left = portrait standard)
- Add OrientationPicker component and wire settings sheet in HomeView
- Add password confirmation field to registration form (RepeatedType)
- Build frontend SPA to public/build/

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

firmware/src/test_display.cpp

@@ -0,0 +1,41 @@
+#ifdef ENV_TEST_DISPLAY
+
+#include <Arduino.h>
+#include <SPI.h>
+#include <LittleFS.h>
+#include "config.h"
+#include "epd.h"
+
+void setup() {
+    Serial.begin(115200);
+    Serial.println("display test boot");
+
+    pinMode(PIN_CS,   OUTPUT);
+    pinMode(PIN_DC,   OUTPUT);
+    pinMode(PIN_RST,  OUTPUT);
+    pinMode(PIN_BUSY, INPUT);
+    SPI.begin(PIN_SCK, -1, PIN_MOSI, PIN_CS);
+    SPI.beginTransaction(SPISettings(4000000, MSBFIRST, SPI_MODE0));
+
+    LittleFS.begin(true);
+
+    File f = LittleFS.open("/img.bin", "r");
+    if (!f) {
+        Serial.println("ERROR: /img.bin not found — did you run uploadfs?");
+        return;
+    }
+    Serial.printf("/img.bin: %u bytes\n", f.size());
+
+    epd_init();
+    epd_draw_image_from_file(f);
+    f.close();
+    epd_sleep();
+
+    Serial.println("done");
+}
+
+void loop() {
+    delay(60000);
+}
+
+#endif