Compose host: restore the original API names PythonLauncher / PythonWidget / PythonAppView #105

Maintainer: the host API was renamed without reason. The original design (app-template pycomposeui/PythonAppView.android.kt, 2023–24) had:

• PythonLauncher(content) — starts Python if needed, registers the current composer with the Python runtime, then composes content;
• PythonWidget(composableName, modifier…, moduleName, content) — composes a named Python composable from a module;
• PythonAppView(modifier…) — composes the module's App.
  Compose host entry point: a @Composable that draws a Python-declared root and recomposes when it is replaced #18 introduced PythonContent(root) / PythonContent(module, attribute) / withPythonComposer instead. Map the current behaviour onto the original names (PythonAppView = the declarative app root incl. state-held roots; PythonWidget = a named Python composable; PythonLauncher = interpreter start + composer registration wrapper), keep the module separate (python-multiplatform core has no Compose dependency; an app that draws Python UI adds this one dependency). Remove the PythonContent names (rule 7: no compatibility aliases). Update SPEC, docs, pythonx-compose callers.
  Completion: the three names exist with the original signatures' intent; all compose fixtures/E2E use them; no PythonContent left.