Add firmware slices 1–2: skeleton and Wi-Fi provisioning

Implement ESP-IDF walking skeleton with SoftAP, health API, and host
tests, then Slice 2 ISecureStore/NvsSecureStore, STA join, POST
/api/wifi, and the provisioning web UI.

Co-authored-by: Cursor <cursoragent@cursor.com>

Software/README.md

@@ -0,0 +1,41 @@
+# DigiRadio Firmware
+
+Open-source Hi-Fi DAB+/FM receiver firmware for the ESP32-S3.
+
+**Status:** Slice 2 — secure store and Wi-Fi STA provisioning.
+
+## Quick start
+
+Open this directory (`Software/`) as the Cursor project so `AGENTS.md` and
+`.cursor/rules/` load automatically.
+
+```bash
+idf.py set-target esp32s3
+idf.py build
+idf.py -p <port> flash monitor
+```
+
+Host unit tests (pure core, no hardware):
+
+```bash
+cmake -S components/core/test -B build-host \
+      -DCMAKE_CXX_COMPILER="$(brew --prefix llvm)/bin/clang++"
+cmake --build build-host
+ctest --test-dir build-host --output-on-failure
+```
+
+Documentation (must exit 0):
+
+```bash
+doxygen Doxyfile
+python3 tools/check-manual-sync.py
+```
+
+## Layout
+
+See [`AGENTS.md`](AGENTS.md) §12 and [`instructions.md`](instructions.md) for
+the authoritative repo layout, coding rules, and development roadmap.
+
+## Licence
+
+Apache-2.0 — see [`LICENSE`](LICENSE).