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>

gui_v6/theme.py

@@ -0,0 +1,83 @@
+"""Thèmes et palette de la GUI V6.
+
+Mappe les tokens de couleur de la maquette ``docs/ui_mockup_v6.html`` vers
+customtkinter. Lot G1 : 4 thèmes de base + helper d'application. L'import de ce
+module ne crée aucun widget (compatible ``--self-test`` sans display).
+"""
+
+from __future__ import annotations
+
+from typing import Dict
+
+# Tokens couleur par thème (bandeau statut licence, accents, surfaces).
+THEMES: Dict[str, dict] = {
+    "clair": {
+        "appearance": "light",
+        "color_theme": "blue",
+        "accent": "#2563eb",
+        "ok": "#16a34a",
+        "warn": "#d97706",
+        "error": "#dc2626",
+    },
+    "sombre": {
+        "appearance": "dark",
+        "color_theme": "blue",
+        "accent": "#3b82f6",
+        "ok": "#22c55e",
+        "warn": "#f59e0b",
+        "error": "#ef4444",
+    },
+    "médical": {
+        "appearance": "light",
+        "color_theme": "green",
+        "accent": "#0d9488",
+        "ok": "#15803d",
+        "warn": "#ca8a04",
+        "error": "#b91c1c",
+    },
+    "contraste": {
+        "appearance": "dark",
+        "color_theme": "dark-blue",
+        "accent": "#60a5fa",
+        "ok": "#4ade80",
+        "warn": "#fbbf24",
+        "error": "#f87171",
+    },
+}
+
+DEFAULT_THEME = "clair"
+
+# Couleurs du bandeau de statut licence selon l'état métier.
+STATUS_COLORS = {
+    "active": "ok",
+    "grace": "warn",
+    "expired": "error",
+    "revoked": "error",
+    "invalid": "error",
+    "unavailable": "warn",
+    "none": "warn",
+}
+
+
+def theme_names() -> list[str]:
+    return list(THEMES.keys())
+
+
+def get_theme(name: str) -> dict:
+    return THEMES.get(name, THEMES[DEFAULT_THEME])
+
+
+def status_color(theme_name: str, status: str) -> str:
+    """Couleur hex pour un statut licence, dans le thème donné."""
+    theme = get_theme(theme_name)
+    return theme[STATUS_COLORS.get(status, "warn")]
+
+
+def apply_theme(name: str = DEFAULT_THEME) -> dict:
+    """Applique le thème à customtkinter. Import paresseux de ctk."""
+    theme = get_theme(name)
+    import customtkinter as ctk
+
+    ctk.set_appearance_mode(theme["appearance"])
+    ctk.set_default_color_theme(theme["color_theme"])
+    return theme