One app fixture for the tests, and ViewModels built where they are used

The tests' `app` fixture, the same two lines in eleven files, now lives once in
tests/conftest.py.

On Android each ViewModel carried a companion `factory` that only wrapped its
constructor in viewModelFactory { initializer { … } }. MainActivity now builds
each one with Compose's viewModel { … } builder, so the five factories and their
imports are gone.

Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>

tests/test_ratelimit.py

@@ -10,7 +10,6 @@ import pytest
 
 from inkwell import ratelimit
 from inkwell.settings import live
-from inkwell.app import create_app
 from inkwell.ratelimit import SlidingWindow
 
 
@@ -28,11 +27,6 @@ def _clean_counters():
     ratelimit.reset_all()
 
 
-@pytest.fixture
-def app():
-    return create_app()
-
-
 def test_under_the_limit_is_not_blocked():
     w = window(3, 60)
     for i in range(3):