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

lib/core/src/app_manager.cpp

@@ -21,19 +21,41 @@ void AppManager::begin() {
     redraw_ = true;
 }
 
-bool AppManager::open(const char* id) {
-    for (auto& info : apps_) {
-        if (std::strcmp(info.id, id) == 0) {
-            switchTo(*info.app);
-            return true;
-        }
-    }
-    return false;
+App* AppManager::find(const char* id) const {
+    for (auto& info : apps_)
+        if (std::strcmp(info.id, id) == 0) return info.app;
+    return nullptr;
 }
 
-void AppManager::home() { switchTo(launcher_); }
+bool AppManager::open(const char* id) {
+    App* app = find(id);
+    if (!app || modal_) return false;
+    switchTo(*app);
+    return true;
+}
+
+void AppManager::home() {
+    if (!modal_) switchTo(launcher_);
+}
+
+bool AppManager::openModal(const char* id) {
+    App* app = find(id);
+    if (!app) return false;
+    switchTo(*app);
+    modal_ = true;
+    return true;
+}
+
+void AppManager::endModal() {
+    modal_ = false;
+    switchTo(launcher_);
+}
 
 void AppManager::handleKey(const KeyEvent& event) {
+    if (modal_) {
+        foreground_->onKey(event);
+        return;
+    }
     if (event.key == Key::Home) {
         home();
         return;
@@ -42,6 +64,12 @@ void AppManager::handleKey(const KeyEvent& event) {
     if (!consumed && event.key == Key::Back) home();
 }
 
+const char* AppManager::foregroundTitle() const {
+    for (auto& info : apps_)
+        if (info.app == foreground_) return info.title;
+    return nullptr;
+}
+
 bool AppManager::takeRedraw() {
     bool r = redraw_ | foreground_->consumeRedraw();
     redraw_ = false;