Intégration station d'impression photo (photostation)

- Icône discrète coin bas-gauche, visible seulement si photostation installée
- Popup PIN (4 chiffres) avant lancement
- Backend : /api/photostation/disponible + /api/photostation/lancer
- kiosk-session.sh : Chromium attend le flag /tmp/photostation_running avant redémarrage
- Script install-photostation.sh pour déploiement sur la Surface

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

backend/main.py

@@ -774,6 +774,39 @@ async def api_supprimer_animation(nom: str):
     return JSONResponse({"erreur": "Fichier introuvable"}, status_code=404)
 
 
+# --- API Photostation ---
+
+FLAG_PHOTOSTATION = Path("/tmp/photostation_running")
+PHOTOSTATION_DIR  = Path("/opt/photostation")
+
+
+@app.get("/api/photostation/disponible")
+async def api_photostation_disponible():
+    disponible = (PHOTOSTATION_DIR / "src" / "main.py").exists()
+    return {"disponible": disponible}
+
+
+@app.post("/api/photostation/lancer")
+async def api_photostation_lancer():
+    if not (PHOTOSTATION_DIR / "src" / "main.py").exists():
+        return JSONResponse({"erreur": "Photostation non installée"}, status_code=404)
+    asyncio.create_task(_lancer_photostation())
+    return {"succes": True}
+
+
+async def _lancer_photostation():
+    FLAG_PHOTOSTATION.touch()
+    await asyncio.sleep(1)
+    # Fermer Chromium (la boucle kiosk attend le flag avant de le relancer)
+    await asyncio.create_subprocess_exec("pkill", "chromium")
+    await asyncio.sleep(2)
+    env = {**__import__("os").environ, "DISPLAY": ":0"}
+    cmd = f"source {PHOTOSTATION_DIR}/venv/bin/activate && python {PHOTOSTATION_DIR}/src/main.py --kiosk"
+    proc = await asyncio.create_subprocess_exec("bash", "-c", cmd, env=env)
+    await proc.wait()
+    FLAG_PHOTOSTATION.unlink(missing_ok=True)
+
+
 # --- API Systeme ---
 
 @app.post("/api/systeme/redemarrer")