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>

sdkconfig.defaults

@@ -0,0 +1,6 @@
+# Shared defaults. Target-specific settings are generated into `sdkconfig`
+# by `idf.py set-target esp32c6` (first-time setup, see README) rather than
+# hardcoded here.
+
+CONFIG_PARTITION_TABLE_CUSTOM=y
+CONFIG_PARTITION_TABLE_CUSTOM_FILENAME="partitions.csv"