feat(04-02): add script download API endpoints and router registration

- imptune/api/scripts.py: GET /printers/{id}/scripts/{install,uninstall,detect}
- 404 for missing printer, 422 for missing driver/INF/driver_desc
- Content-Disposition attachment header on all responses
- imptune/main.py: register scripts.router
- 5 integration tests covering all endpoint cases (200/404/422)

imptune/main.py

@@ -5,7 +5,7 @@ from pathlib import Path
 from fastapi import FastAPI
 from fastapi.staticfiles import StaticFiles
 
-from imptune.api import clients, drivers, health, pages, printers
+from imptune.api import clients, drivers, health, pages, printers, scripts
 from imptune.config import DATA_DIR, DRIVERS_DIR
 from imptune.db.database import db, init_db
 
@@ -33,3 +33,4 @@ app.include_router(pages.router)
 app.include_router(drivers.router)
 app.include_router(printers.router)
 app.include_router(clients.router)
+app.include_router(scripts.router)