[core] Use placement new for global Application instance

Replace the global `Application App` with placement-new construction
in aligned .bss storage. This eliminates the global constructor and
destructor chain that were:

- Calling xSemaphoreCreateMutex() at static init time (via Scheduler's
  Mutex member) before app_main() runs
- Redundantly zero-initializing all members that .bss already zeroes
- Registering __cxa_atexit for ~Application() destructor chain
  (~Application, ~vector, ~Mutex) that never runs on embedded

The storage is a char[] with a GCC asm label matching the mangled name
of esphome::App. Other translation units see a typed extern Application
(identical codegen, no indirection), while the defining TU sees a
trivially-destructible char array — so the compiler never emits
__cxa_atexit or the destructor chain.

Construction happens in pre_setup() via placement new, which is always
the first method called on App in the generated setup() function.

esphome/core/application.cpp

@@ -669,7 +669,14 @@ void Application::yield_with_select_(uint32_t delay_ms) {
 #endif
 }
 
-Application App;  // NOLINT(cppcoreguidelines-avoid-non-const-global-variables)
+// App storage — asm label shares the linker symbol with "extern Application App".
+// char[] is trivially destructible, so no __cxa_atexit or destructor chain is emitted.
+// Constructed via placement new in the generated setup().
+#ifndef __GXX_ABI_VERSION
+#error "Application placement new requires Itanium C++ ABI (GCC/Clang)"
+#endif
+// NOLINTNEXTLINE(cppcoreguidelines-avoid-non-const-global-variables)
+alignas(Application) char app_storage[sizeof(Application)] asm("_ZN7esphome3AppE");
 
 #if defined(USE_SOCKET_SELECT_SUPPORT) && defined(USE_WAKE_LOOP_THREADSAFE)
 void Application::setup_wake_loop_threadsafe_() {

esphome/core/config.py

@@ -512,6 +512,9 @@ async def to_code(config: ConfigType) -> None:
     cg.add_global(cg.RawExpression("using std::min"))
     cg.add_global(cg.RawExpression("using std::max"))
 
+    # Construct App via placement new — see application.cpp for storage details
+    cg.add_global(cg.RawExpression("#include <new>"))
+    cg.add(cg.RawExpression("new (&App) Application()"))
     cg.add(
         cg.App.pre_setup(
             config[CONF_NAME],