M0 step 7: Settings, About, Storage, first-boot setup

- lib/apps_model (host-tested): SettingsMenu (rows, readable values,
  choices, validation messages) and SetupWizard (names, Region
  confirmation, timezone; saves only when finished)
- AppManager: modal Apps that Home/Back can't leave (setup wizard)
- SettingsApp: all settings plus Storage (usage, erase SD behind a
  dialog) and About (version, node id, battery, memory, uptime) pages,
  replacing the temporary Diagnostics App
- SetupApp: first-boot wizard, opened modally until SetupDone
- Node id and default names derived from the MAC like Meshtastic
- Widget demo is now hidden (About, then w)
- lib_ldf_mode = deep+ so libraries see each other's headers

Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_01EhqxQ49eCju4CzKYNjZzwT

test/test_app_manager/test_app_manager.cpp

@@ -155,6 +155,32 @@ void test_update_reaches_only_the_foreground_app() {
     TEST_ASSERT_EQUAL(0, f.launcher.lastUpdate);
 }
 
+void test_modal_app_keeps_home_and_back() {
+    Fixture f;
+    f.manager.openModal("demo");
+    f.manager.handleKey(KeyEvent::of(Key::Home));
+    f.manager.handleKey(KeyEvent::of(Key::Back));
+    TEST_ASSERT_EQUAL_PTR(&f.demo, &f.manager.foreground());
+    TEST_ASSERT_EQUAL(2, f.demo.keys.size());  // both reached the App
+}
+
+void test_ending_the_modal_returns_to_launcher_and_unlocks_home() {
+    Fixture f;
+    f.manager.openModal("demo");
+    f.manager.endModal();
+    TEST_ASSERT_EQUAL_PTR(&f.launcher, &f.manager.foreground());
+    f.manager.open("notes");
+    f.manager.handleKey(KeyEvent::of(Key::Home));
+    TEST_ASSERT_EQUAL_PTR(&f.launcher, &f.manager.foreground());
+}
+
+void test_modal_app_cannot_be_switched_away_by_open() {
+    Fixture f;
+    f.manager.openModal("demo");
+    TEST_ASSERT_FALSE(f.manager.open("notes"));
+    TEST_ASSERT_EQUAL_PTR(&f.demo, &f.manager.foreground());
+}
+
 int main() {
     UNITY_BEGIN();
     RUN_TEST(test_launcher_is_in_foreground_after_begin);
@@ -170,5 +196,8 @@ int main() {
     RUN_TEST(test_switching_apps_requests_a_redraw);
     RUN_TEST(test_app_can_request_its_own_redraw);
     RUN_TEST(test_update_reaches_only_the_foreground_app);
+    RUN_TEST(test_modal_app_keeps_home_and_back);
+    RUN_TEST(test_ending_the_modal_returns_to_launcher_and_unlocks_home);
+    RUN_TEST(test_modal_app_cannot_be_switched_away_by_open);
     return UNITY_END();
 }