Scaffold NCS firmware project structure

Sets up kvida-os as a freestanding nRF Connect SDK application for the
nRF54L15, pinned to NCS v3.4.0, with a Docker/WSL2 build environment
(toolchain-only image, NCS modules fetched into a separate volume at
first run) and placeholder module directories matching the architecture
described in the kvida meta-repo.

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

app/src/hal/README.md

@@ -0,0 +1,3 @@
+# hal
+
+Hardware abstraction layer: wraps nRF54L15 peripherals (GPIO, ADC, I2C) behind a board-independent interface used by the other modules.