OTA steps 3-5: Update Service, Probation and Rollback, Update from SD

- EcdsaVerifier (mbedTLS, embedded public key) and EspOtaSink (writes
  the inactive app slot, esp_ota_end validates the image, then sets
  the boot partition)
- UpdateService: listens on TCP 3232 (and mDNS roro9stack-<id>) while
  Wi-Fi is Connected; streams into UpdateParser; replies OK/ERR to the
  sender; remembers the pending version so a Rollback is reported
  after the reboot
- Probation (host-tested): confirm after the first frame + 30 s + Wi-Fi
  (if configured); roll back if configured Wi-Fi never connects in 3 min
- Main loop: full-screen progress while receiving; restart once
  installed, waiting up to 60 s for Text Entry to end
- Settings > Firmware: version, Probation status, push address and
  name, and the .ota files in /updates on the SD card to install
- StorageService.runJob() runs work on the storage task (SD installs)
- wifi status prints IP and running version; RORO_TEST_CRASH test hook

Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_01EhqxQ49eCju4CzKYNjZzwT

src/platform/ota_device.h

@@ -0,0 +1,38 @@
+#pragma once
+
+#include <esp_ota_ops.h>
+#include <mbedtls/pk.h>
+
+#include "update_parser.h"
+
+namespace roro {
+
+// Checks Update File signatures against the public key compiled into the firmware (ADR 0003).
+class EcdsaVerifier : public SignatureVerifier {
+   public:
+    EcdsaVerifier();
+    ~EcdsaVerifier() override;
+    bool verify(const uint8_t digest[32], const uint8_t* signature, size_t len) override;
+
+   private:
+    mbedtls_pk_context key_;
+    bool ready_ = false;
+};
+
+// Writes the image to the app slot that isn't running, and makes it the next boot on finish().
+class EspOtaSink : public UpdateSink {
+   public:
+    EspOtaSink() : slot_(esp_ota_get_next_update_partition(nullptr)) {}
+    size_t capacity() const { return slot_ ? slot_->size : 0; }
+    bool begin(size_t imageSize) override;
+    bool write(const uint8_t* data, size_t len) override;
+    bool finish() override;
+    void abort() override;
+
+   private:
+    const esp_partition_t* slot_;
+    esp_ota_handle_t handle_ = 0;
+    bool open_ = false;
+};
+
+}  // namespace roro