feat(gui): add GUI V6 G1 foundation (license client/store, shell, About tab)

Socle de la refonte GUI V6 (couche présentation uniquement, aucune logique de
détection) :
- license_store: stockage licence hors dépôt (%LOCALAPPDATA%/Aivanov | XDG),
  read/write atomique/delete, ne journalise aucun token
- license_client: LicenseStatus + activate/check/local_status, session HTTP
  injectable, serveur indisponible géré sans crash, aucune clé privée
- theme: 4 thèmes + couleurs de statut licence
- app + tab_about: shell customtkinter minimal (header, bandeau licence,
  3 onglets), onglet À propos étoffé
- Pseudonymisation_Gui_V6.py: point d'entrée + --self-test (exit 0 sans fenêtre)
- requirements.txt: customtkinter==5.2.2

Tests: 20 nouveaux (store sur vrais fichiers, client sur session injectée).
Suite tests/unit: 167 passed, 0 régression. V5/moteur/managers/specs intacts.

Co-Authored-By: Claude Opus 4.8 (1M context) <noreply@anthropic.com>

tests/unit/test_gui_v6_license_store.py

@@ -0,0 +1,91 @@
+"""Tests du stockage local de licence (vrais fichiers, aucun mock).
+
+Couvre : résolution du chemin par plateforme, round-trip save/load, création
+du répertoire parent, suppression, robustesse au JSON corrompu.
+"""
+
+from __future__ import annotations
+
+import json
+from pathlib import Path
+
+import pytest
+
+from gui_v6.license_store import LicenseStore, default_license_path
+
+
+def test_default_path_windows(monkeypatch):
+    monkeypatch.setattr("sys.platform", "win32")
+    monkeypatch.setenv("LOCALAPPDATA", r"C:\Users\dom\AppData\Local")
+    path = default_license_path()
+    parts = path.as_posix()
+    assert parts.endswith("Aivanov/Anonymisation/license.json")
+
+
+def test_default_path_linux(monkeypatch):
+    monkeypatch.setattr("sys.platform", "linux")
+    monkeypatch.delenv("XDG_DATA_HOME", raising=False)
+    monkeypatch.setattr(Path, "home", classmethod(lambda cls: Path("/home/tester")))
+    path = default_license_path()
+    assert path == Path("/home/tester/.local/share/aivanov/anonymisation/license.json")
+
+
+def test_default_path_linux_respects_xdg(monkeypatch):
+    monkeypatch.setattr("sys.platform", "linux")
+    monkeypatch.setenv("XDG_DATA_HOME", "/custom/data")
+    path = default_license_path()
+    assert path == Path("/custom/data/aivanov/anonymisation/license.json")
+
+
+def test_save_creates_parent_dir_and_roundtrips(tmp_path):
+    target = tmp_path / "nested" / "dir" / "license.json"
+    store = LicenseStore(target)
+    assert not store.exists()
+
+    payload = {"status": "active", "license_ref": "LIC-123", "expires_at": "2027-01-01"}
+    store.save(payload)
+
+    assert target.is_file()
+    assert store.exists()
+    assert store.load() == payload
+    # Vérifie aussi le contenu sur disque (vrai fichier JSON).
+    on_disk = json.loads(target.read_text(encoding="utf-8"))
+    assert on_disk["license_ref"] == "LIC-123"
+
+
+def test_load_absent_returns_none(tmp_path):
+    store = LicenseStore(tmp_path / "absent.json")
+    assert store.load() is None
+
+
+def test_load_corrupted_returns_none(tmp_path):
+    target = tmp_path / "license.json"
+    target.write_text("{ this is not valid json", encoding="utf-8")
+    store = LicenseStore(target)
+    assert store.load() is None
+
+
+def test_load_non_object_returns_none(tmp_path):
+    target = tmp_path / "license.json"
+    target.write_text("[1, 2, 3]", encoding="utf-8")
+    store = LicenseStore(target)
+    assert store.load() is None
+
+
+def test_delete(tmp_path):
+    target = tmp_path / "license.json"
+    store = LicenseStore(target)
+    store.save({"status": "active"})
+    assert store.delete() is True
+    assert not target.exists()
+    # Suppression idempotente : un second delete ne lève pas.
+    assert store.delete() is False
+
+
+def test_save_overwrites(tmp_path):
+    store = LicenseStore(tmp_path / "license.json")
+    store.save({"status": "active", "v": 1})
+    store.save({"status": "grace", "v": 2})
+    loaded = store.load()
+    assert loaded["status"] == "grace"
+    assert loaded["v"] == 2