Step 2b: firmware upload (/api/ota) with image checks and rollback self-test

- aes67_ota: GET /api/ota (version, project, build_date, idf, running,
  previous, previous_version, pending_verify, can_rollback), POST
  /api/ota streamed into the inactive slot (4 KiB chunks), POST
  /api/ota/confirm and /api/ota/rollback.
- Rejected before any flash write: bad magic, wrong chip, wrong
  project_name, chip revision outside the image's min/max range.
  esp_ota_end verifies the whole image.
- Self-test on a pending image: IP address plus HTTP 200 from our own
  /api/status within 60 s marks it valid; otherwise mark invalid and
  reboot into the previous slot. A crash before that is rolled back by
  the bootloader.
- CONFIG_AES67_OTA_SELFTEST_FORCE_FAIL (test builds only) forces a
  failed self-test.
- aes67_web: web_reboot_later() shared by /api/reboot and OTA.

Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>

main/CMakeLists.txt

@@ -1,5 +1,5 @@
 idf_component_register(SRCS "main.c" "project_cfg.c"
                        INCLUDE_DIRS "."
                        REQUIRES esp_app_format esp_hw_support
-                                aes67_board aes67_health aes67_net aes67_ptp
+                                aes67_board aes67_health aes67_net aes67_ota aes67_ptp
                                 aes67_syslog aes67_tx aes67_web)