feat: switch iperf3 to JNI with 3.19 source

- Switch from bundled iperf3 binary (Process.start) to JNI compilation
- iperf3 3.21 source API was incompatible (start_time, iperf_strerror, etc.)
- iperf3 3.19 source is proven to work (used by CellularLab)
- CMakeLists.txt updated: config.h generated into cpp/iperf/ for correct include paths
- iperf_jni.c fixed for 3.19 API (no start_time on iperf_test)
- getTestProgress() returns g_test->duration as fallback (no real-time elapsed tracking yet)
- NDK CMake pinned to 3.22.1
- UI layer updated: removed Iperf3BinaryPathProvider references
- Tests updated: TestRunViewModelTest matches new service interface
- pubspec.yaml: removed iperf3 assets bundle, added http dependency
- AndroidManifest: INTERNET permission (needed for hostname resolution)

android/app/src/main/cpp/CMakeLists.txt

@@ -0,0 +1,74 @@
+cmake_minimum_required(VERSION 3.22.1)
+project("iperf3jni")
+
+# ──────────────────────────────────────────────────────────────────
+# Paths
+# ──────────────────────────────────────────────────────────────────
+# CMAKE_SOURCE_DIR here is android/app/src/main/cpp/
+set(IPERF_SRC_DIR ${CMAKE_SOURCE_DIR}/iperf)
+
+# ──────────────────────────────────────────────────────────────────
+# Generate iperf_config.h from our Android template, into cpp/iperf/
+# (iperf.h uses #include "iperf_config.h" which resolves relative to its dir)
+# ──────────────────────────────────────────────────────────────────
+configure_file(
+    ${IPERF_SRC_DIR}/iperf_config_android.h
+    ${IPERF_SRC_DIR}/iperf_config.h
+)
+
+# ──────────────────────────────────────────────────────────────────
+# Shared library: iperf3jni
+# ──────────────────────────────────────────────────────────────────
+add_library(iperf3jni SHARED
+
+    # JNI bridge (directly in cpp/)
+    iperf_jni.c
+
+    # iperf3 source files (in cpp/iperf/)
+    iperf/iperf_api.c
+    iperf/iperf_client_api.c
+    iperf/iperf_util.c
+    iperf/iperf_udp.c
+    iperf/iperf_tcp.c
+    iperf/iperf_server_api.c
+    iperf/iperf_sctp.c
+    iperf/iperf_error.c
+    iperf/iperf_time.c
+    iperf/iperf_locale.c
+    iperf/iperf_pthread.c
+    iperf/iperf_auth.c
+    iperf/net.c
+    iperf/timer.c
+    iperf/units.c
+    iperf/cjson.c
+    iperf/dscp.c
+    iperf/tcp_info.c
+)
+
+# ──────────────────────────────────────────────────────────────────
+# Include directories - iperf/ FIRST so "iperf_config.h" resolves there
+# ──────────────────────────────────────────────────────────────────
+target_include_directories(iperf3jni PRIVATE
+    ${IPERF_SRC_DIR}             # for iperf headers (iperf_config.h, iperf.h, etc.)
+    ${CMAKE_SOURCE_DIR}          # for JNI includes
+)
+
+# ──────────────────────────────────────────────────────────────────
+# Compile definitions
+# ──────────────────────────────────────────────────────────────────
+target_compile_definitions(iperf3jni PRIVATE
+    HAVE_PTHREAD
+    __ANDROID__
+    # Disable the main() entry point — we're a shared lib, not a standalone binary
+    IPERF_JNI_BUILD=1
+)
+
+# ──────────────────────────────────────────────────────────────────
+# Link libraries
+# ──────────────────────────────────────────────────────────────────
+find_package(Threads REQUIRED)
+target_link_libraries(iperf3jni
+    Threads::Threads
+    log
+    android
+)