Convert to external .fap; export ST BLE command API from the firmware

build.sh now adds ST's aci_*/hci_* headers to the SDK (with extern "C"
guards, the API table is C++), lets fbt regenerate api_symbols.csv and
enables the selected functions (BLE_API=hci,gatt default; min; all).
The app builds as a normal .fap shipped inside the update package and
loadable from SD, saving ~12 KB of firmware flash versus the built-in
(min mode: ~22 KB). qsort replaced with an insertion sort since libc's
qsort is not exported to apps. README documents modes and flash budget.

bt_inspector/application.fam

@@ -1,12 +1,16 @@
-# Built-in (firmware-linked) app: it needs the ST GAP/GATT/HCI command API,
-# which the firmware does not export to .fap apps. See ../build.sh.
+# External app. Needs firmware built by ../build.sh: full BLE stack plus the
+# ST aci_*/hci_* command API exported to apps.
 App(
     appid="bt_inspector",
     name="BT Inspector",
-    apptype=FlipperAppType.APP,
+    apptype=FlipperAppType.EXTERNAL,
     entry_point="bt_inspector_app",
     requires=["gui", "storage"],
     stack_size=4 * 1024,
-    icon="A_Plugins_14",
-    order=25,
+    fap_category="Bluetooth",
+    fap_icon="icon.png",
+    fap_version="1.0",
+    fap_description="BLE scanner and GATT explorer (full-stack firmware)",
+    fap_author="andydixon",
+    fap_weburl="https://github.com/andydixon/flipper-bt-inspector",
 )