firmware: build fixes — esp_app_format component + forward-declare s_last_painted_seq

Two build breaks discovered when actually compiling the prior commits:

- main/CMakeLists.txt missing esp_app_format requirement, so
  esp_app_desc.h couldn't be resolved when app_main.c included it for
  the boot-time git-hash log.

- s_last_painted_seq is referenced inside state_post_handler (reset
  to 0 on /state wake) but the static was declared further down the
  file alongside the other /frame state. C requires declaration
  before use — forward declare it above state_post_handler and keep
  a stub comment at the original location.

0 files changed, 0 insertions, 0 deletions