Firmware version from version.txt (0.9.0) instead of git describe

The version is now set by hand in version.txt, so it's readable and only
changes on purpose. git describe gave commit hashes, and always "-dirty"
because the build applies patches to the cspot submodule. Editing the file
is enough; the next build picks it up.

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

CMakeLists.txt

@@ -1,20 +1,9 @@
 cmake_minimum_required(VERSION 3.16)
 
-# Firmware version = git describe (tags, dirty flag). Reported by esp_app_get_description()
-# and in status.fw / GET /api/ota. CMake re-runs when git's HEAD log or index changes (commit,
-# checkout, add), so the version follows. A new tag or unstaged edits need `idf.py reconfigure`.
-set_property(DIRECTORY APPEND PROPERTY CMAKE_CONFIGURE_DEPENDS
-    ${CMAKE_CURRENT_LIST_DIR}/.git/logs/HEAD
-    ${CMAKE_CURRENT_LIST_DIR}/.git/index)
-execute_process(
-    COMMAND git describe --tags --always --dirty
-    WORKING_DIRECTORY ${CMAKE_CURRENT_LIST_DIR}
-    OUTPUT_VARIABLE PROJECT_VER
-    OUTPUT_STRIP_TRAILING_WHITESPACE
-    ERROR_QUIET)
-if(NOT PROJECT_VER)
-    set(PROJECT_VER "0.0.0-nogit")
-endif()
+# Firmware version = the first line of version.txt (edit it to release a new version). Reported by
+# esp_app_get_description() and in status.fw / GET /api/ota. Editing the file re-runs CMake.
+set_property(DIRECTORY APPEND PROPERTY CMAKE_CONFIGURE_DEPENDS ${CMAKE_CURRENT_LIST_DIR}/version.txt)
+file(STRINGS ${CMAKE_CURRENT_LIST_DIR}/version.txt PROJECT_VER LIMIT_COUNT 1)
 
 include($ENV{IDF_PATH}/tools/cmake/project.cmake)
 project(aes67_p4)