Add settings screen and adult space with progress report and save export/restore (0.4.0)

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

tests/settings/test_app_settings.gd

@@ -0,0 +1,37 @@
+extends GutTest
+## Tests d'AppSettings : valeurs par defaut, nettoyage des fichiers abimes,
+## conversions volume/echelle de texte.
+
+
+func test_defaults_are_usable() -> void:
+    var settings := AppSettings.defaults()
+    assert_true(settings["animations_enabled"])
+    assert_eq(AppSettings.text_scale(settings), 1.0)
+
+
+func test_sanitize_of_non_dictionary_gives_defaults() -> void:
+    assert_eq(AppSettings.sanitize("n'importe quoi"), AppSettings.defaults())
+    assert_eq(AppSettings.sanitize(null), AppSettings.defaults())
+
+
+func test_sanitize_clamps_out_of_range_values() -> void:
+    var clean := AppSettings.sanitize(
+        {"volume": 7.0, "text_scale_index": 99, "animations_enabled": false}
+    )
+    assert_eq(clean["volume"], 1.0)
+    assert_eq(clean["text_scale_index"], AppSettings.TEXT_SCALES.size() - 1)
+    assert_false(clean["animations_enabled"])
+    assert_eq(AppSettings.sanitize({"volume": -2})["volume"], 0.0)
+
+
+func test_sanitize_ignores_wrong_types() -> void:
+    var clean := AppSettings.sanitize(
+        {"volume": "fort", "text_scale_index": "grand", "animations_enabled": "oui"}
+    )
+    assert_eq(clean, AppSettings.defaults())
+
+
+func test_zero_volume_is_real_silence() -> void:
+    assert_eq(AppSettings.volume_db(0.0), -80.0)
+    assert_eq(AppSettings.volume_db(1.0), 0.0)
+    assert_lt(AppSettings.volume_db(0.5), 0.0)