Add BT Inspector: BLE scanner and GATT explorer for Flipper Zero

Built-in firmware app (needs the full ST BLE stack) with live RSSI-sorted
scan list, advertisement decoding (Apple Continuity, Microsoft CDP, Fast
Pair, Eddystone), connect/discover/read/write/notify, device-info summary,
value history and a timestamped session log. build.sh produces a firmware
update package with COPRO_STACK_TYPE=ble_full and the app compiled in.

build.sh

@@ -0,0 +1,68 @@
+#!/usr/bin/env bash
+# Build a Flipper Zero firmware update package that contains BT Inspector.
+#
+# Why a firmware build and not a plain .fap:
+#   * The stock radio coprocessor image is ST's "BLE Light" stack: peripheral/
+#     broadcaster only. Scanning and connecting as a central need the "full"
+#     stack (COPRO_STACK_TYPE=ble_full, already supported by fbt).
+#   * The firmware does not export the ST GAP/GATT/HCI command API to external
+#     apps, so the app is compiled in as a built-in ("--extra-int-apps").
+#
+# Usage:
+#   ./build.sh            build  -> flipperzero-firmware/dist/f7-C/f7-update-*/ (update package)
+#   ./build.sh flash      build and flash over USB (Flipper connected, qFlipper closed)
+#   FW_TAG=1.4.3 ./build.sh   pin a different firmware tag (default 1.4.3)
+#   JOBS=2 ./build.sh         limit parallel compile jobs (default 4)
+set -euo pipefail
+
+HERE="$(cd "$(dirname "${BASH_SOURCE[0]}")" && pwd)"
+APP_SRC="$HERE/bt_inspector"
+FW_DIR="${FW_DIR:-$HERE/flipperzero-firmware}"
+FW_TAG="${FW_TAG:-1.4.3}"
+FW_REPO="https://github.com/flipperdevices/flipperzero-firmware.git"
+
+if [ ! -d "$FW_DIR/.git" ]; then
+    echo ">> cloning firmware $FW_TAG into $FW_DIR"
+    git clone --depth 1 --branch "$FW_TAG" --recurse-submodules --shallow-submodules "$FW_REPO" "$FW_DIR"
+fi
+
+cd "$FW_DIR"
+
+# Let GAP take the central/observer roles as well as peripheral (harmless on the
+# full stack; the app itself uses HCI-level scan/connect commands).
+GAP_C=targets/f7/ble_glue/gap.c
+if grep -q "^        GAP_PERIPHERAL_ROLE,$" "$GAP_C"; then
+    sed -i 's/^        GAP_PERIPHERAL_ROLE,$/        GAP_PERIPHERAL_ROLE | GAP_CENTRAL_ROLE | GAP_OBSERVER_ROLE,/' "$GAP_C"
+    echo ">> patched $GAP_C: GAP roles = peripheral|central|observer"
+fi
+
+# Link (or refresh) the app into the user apps directory.
+mkdir -p applications_user
+rm -rf applications_user/bt_inspector
+cp -r "$APP_SRC" applications_user/bt_inspector
+
+FBT_ARGS=(
+    COMPACT=1 DEBUG=0 # release build, same as official images
+    COPRO_STACK_TYPE=ble_full
+    COPRO_STACK_BIN=stm32wb5x_BLE_Stack_full_fw.bin
+    --extra-int-apps=bt_inspector
+)
+
+echo ">> building update package (full BLE stack + BT Inspector)"
+./fbt -j"${JOBS:-4}" "${FBT_ARGS[@]}" updater_package
+
+PKG=$(ls -d dist/f7-C/f7-update-* 2>/dev/null | head -1)
+echo
+echo ">> update package: $PKG"
+echo ">> radio stack in package:"
+grep -E "^Radio" "$PKG/update.fuf" || true
+echo ">> firmware size:"
+ls -l "$PKG/firmware.dfu"
+echo
+echo "Install: copy '$PKG' to the SD card (e.g. /ext/update/) and run it from"
+echo "the file browser, or use: ./build.sh flash"
+
+if [ "${1:-}" = "flash" ]; then
+    echo ">> flashing over USB"
+    ./fbt -j"${JOBS:-4}" "${FBT_ARGS[@]}" flash_usb_full
+fi