fix(setup,ui): risolve errori setup + logo SVG theme-aware

- setup: corregge path templates (sibling di api/, non figlio) e firma TemplateResponse
- setup: invalida sessione client dopo operazioni che ruotano l'API key (init DB, creazione admin, cambio password, attivazione utente)
- api_client: include il nome del campo nei messaggi di errore 422 (FastAPI validation)
- ui: nuovo componente _app_logo.html (SVG inline theme-aware) usato su login e navbar

src/backend/api/routers/setup.py

@@ -26,7 +26,7 @@ from src.backend.services.measurement_service import calculate_pass_fail
 
 router = APIRouter(prefix="/api/setup", tags=["setup"])
 
-_templates_dir = Path(__file__).resolve().parent.parent / "templates"
+_templates_dir = Path(__file__).resolve().parent.parent.parent / "templates"
 templates = Jinja2Templates(directory=str(_templates_dir))
 
 
@@ -215,7 +215,7 @@ async def _seed_default_station(session: AsyncSession, admin_user: User) -> None
 async def setup_page(request: Request):
     """Serve the setup page HTML."""
     _check_setup_enabled()
-    return templates.TemplateResponse("setup/setup.html", {"request": request})
+    return templates.TemplateResponse(request, "setup/setup.html")
 
 
 @router.get("/status")