Rebuild firmware scaffold for ESP32-C6/ESP-IDF, replacing NCS/Zephyr

The product pivoted away from a Matter-first nRF54L15 device to an
ESP32-C6/ESP-IDF/C++17 platform where behaviour is defined by a
Blockly-generated Lua program instead of custom firmware (see the
updated kvida meta-repo vision). Removes the west/NCS/Zephyr scaffold
and replaces it with:

- A pinned ESP-IDF v6.0.2 Docker build environment (Espressif's
  official image already bundles the toolchain, unlike NCS/west).
- A layered component structure (drivers -> sensors -> profiles ->
  lua_runtime -> transport) matching the new architecture principles,
  with per-component READMEs describing responsibilities.
- An A/B OTA + LittleFS partition table and a minimal main.cpp.

Co-Authored-By: Claude Sonnet 5 <noreply@anthropic.com>

test/README.md

@@ -0,0 +1,7 @@
+# test
+
+Host-based unit tests for business logic that doesn't need real hardware, per the testing philosophy in `AGENTS.md`: "Everything that can be tested on a desktop should be."
+
+Primary candidates once they have real code: `components/sensors`, `components/profiles`, and the non-hardware parts of `components/lua_runtime` (Lua sandboxing/API surface, not GPIO access).
+
+ESP-IDF supports building against its `linux` target (`idf.py --preview set-target linux`) to run component unit tests on the host without a board. No test scaffolding is wired up yet since there's no logic to test.