Phase 3 : hardening qualite de code - typage strict, securite, dead code, a11y

Config strictement stricte partout (ruff, mypy --strict, bandit, vulture,
import-linter, eslint, stylelint), aucune regle desactivee "pour ne pas
casser le build" - l'existant a ete corrige pour la satisfaire plutot que
l'inverse. Hooks pre-commit locaux (language: system) bloquants.

- Typage mypy --strict propage a tout le moteur (db, screens, auth, core,
  ai, routes, puis publish/scripts/tests/app.py/build_css.py).
- Securite : fuite de handle fichier Windows corrigee dans l'export SCORM
  (routes/publish/export_scorm.py), CSRF/RNG non-crypto/xAPI documentes
  (# nosec, # NOSONAR justifies), nouveau db.json_for_script() (echappe
  "</script>" dans le JSON embarque en <script>, 25 sites).
- Architecture : imports circulaires/F811 nettoyes, contrats
  import-linter respectes, code mort retire (vulture).
- Accessibilite : 69 champs de formulaire sans label correctement
  associe corriges (for/id ou aria-label) sur 11 templates.
- ESLint/Stylelint : lot mecanique JS/CSS, regles ajustees puis
  appliquees (aucune desactivee sans verification individuelle).
- Tests : isolation du compte admin partage (nettoyage ponctuel +
  fixture de teardown automatique en filet de securite), suite complete
  verte (591 tests Python, 241 tests JS).
- SonarQube Community Build self-heberge (Docker + PostgreSQL) : rapport
  complet analyse point par point, faux positifs documentes.
- .gitattributes ajoute (LF force) : core.autocrlf=true sur cette machine
  faisait echouer ESLint (linebreak-style) via un bug connu de git
  (checkout "en place" qui ignore l'eol force sur un fichier deja
  present sur disque - contourne en supprimant puis recreant chaque
  fichier suivi).

djLint (H021, styles inline) volontairement saute pour ce commit -
backlog assume, deja documente, traite dans un lot separe.

Co-Authored-By: Claude Sonnet 5 <noreply@anthropic.com>

tests/test_sound.py

@@ -4,20 +4,24 @@ son" (effet sonore, non bouclé). Comme le reste du graphe de logique côté
 client, la lecture audio RÉELLE n'est pas testable sans navigateur (voir
 play_js_bundle() — on vérifie que la logique existe dans le JS livré et que
 les données persistent, pas qu'elles jouent un son)."""
+
 import json
 import re
+from typing import Any
 
-from conftest import play_js_bundle
+from conftest import play_js_bundle  # type: ignore[import-not-found]  # resolu par pytest, pas mypy
+from flask.testing import FlaskClient
 
 import screens
+from tests.conftest import not_none
 
 
-def _create_screen(client, slug, name="Accueil"):
+def _create_screen(client: FlaskClient, slug: str, name: str = "Accueil") -> Any:
     resp = client.post(f"/game/{slug}/screens/new", data={"name": name}, follow_redirects=False)
-    return int(re.search(r"/screens/(\d+)/edit", resp.headers["Location"]).group(1))
+    return int(not_none(re.search(r"/screens/(\d+)/edit", resp.headers["Location"])).group(1))
 
 
-def _add_flow_node(client, slug, screen_id, **fields):
+def _add_flow_node(client: FlaskClient, slug: str, screen_id: int, **fields: Any) -> Any:
     resp = client.post(
         f"/game/{slug}/screens/{screen_id}/flow/nodes/add",
         data=json.dumps(fields),
@@ -27,7 +31,7 @@ def _add_flow_node(client, slug, screen_id, **fields):
     return resp.get_json()["id"]
 
 
-def test_screen_background_music_persists(client, game):
+def test_screen_background_music_persists(client: FlaskClient, game: str) -> None:
     screen_id = _create_screen(client, game)
     resp = client.post(
         f"/game/{game}/screens/{screen_id}/background-music",
@@ -35,11 +39,11 @@ def test_screen_background_music_persists(client, game):
         content_type="application/json",
     )
     assert resp.status_code == 200
-    screen = screens.get_screen(game, screen_id)
+    screen = not_none(screens.get_screen(game, screen_id))
     assert screen["background_music_url"] == "https://example.com/song.mp3"
 
 
-def test_screen_background_music_empty_string_clears_it(client, game):
+def test_screen_background_music_empty_string_clears_it(client: FlaskClient, game: str) -> None:
     screen_id = _create_screen(client, game)
     client.post(
         f"/game/{game}/screens/{screen_id}/background-music",
@@ -51,11 +55,11 @@ def test_screen_background_music_empty_string_clears_it(client, game):
         data=json.dumps({"url": ""}),
         content_type="application/json",
     )
-    screen = screens.get_screen(game, screen_id)
+    screen = not_none(screens.get_screen(game, screen_id))
     assert screen["background_music_url"] is None
 
 
-def test_play_payload_exposes_background_music_per_screen(client, game):
+def test_play_payload_exposes_background_music_per_screen(client: FlaskClient, game: str) -> None:
     screen_id = _create_screen(client, game)
     client.post(
         f"/game/{game}/screens/{screen_id}/background-music",
@@ -67,25 +71,29 @@ def test_play_payload_exposes_background_music_per_screen(client, game):
     assert screen_payload["background_music_url"] == "https://example.com/song.mp3"
 
 
-def test_sound_action_node_persists_url(client, game):
+def test_sound_action_node_persists_url(client: FlaskClient, game: str) -> None:
     screen_id = _create_screen(client, game)
     node_id = _add_flow_node(
-        client, game, screen_id, node_type="action", action_type="jouer_son",
+        client,
+        game,
+        screen_id,
+        node_type="action",
+        action_type="jouer_son",
         data_value="https://example.com/effect.wav",
     )
-    node = screens.get_flow_node(game, node_id)
+    node = not_none(screens.get_flow_node(game, node_id))
     assert node["action_type"] == "jouer_son"
     assert node["data_value"] == "https://example.com/effect.wav"
 
 
-def test_play_page_exposes_sound_runtime(client, game):
+def test_play_page_exposes_sound_runtime(client: FlaskClient, game: str) -> None:
     js = play_js_bundle()
     assert "runScreenBackgroundMusic" in js
     assert "'jouer_son'" in js
     assert "new Audio" in js
 
 
-def test_scene_editor_exposes_sound_action(client, game):
+def test_scene_editor_exposes_sound_action(client: FlaskClient, game: str) -> None:
     """L'UI de réglage de la musique de fond par écran (screen-bg-music-url)
     et le formulaire générique de nœud d'action (nf-action-sound-fields)
     n'existaient que dans l'éditeur document, retiré — l'action "Jouer un