Improvements and fixes

Renaming a sensor and re-reading a data logger no longer fail with an error, and assistant-filed tickets show their category.

• An irradiation sensor can again be renamed on the plant's "Components" page.
• Re-probing a data logger no longer fails its login when no new credentials are entered.
• A ticket the assistant files no longer appears without its category icon and label.
• A webhook entered in notification settings is now checked first — name, URL, and headers — with a wrong value shown instead of an error.