fix(firearms): creating and editing a firearm report the error with the deleteFailed key

[seketman]

Problem

createFirearm and updateFirearm report their operation's error using the translation key for deletion:

// src/lib/actions/firearms.ts:60  (createFirearm)
if (error) redirectWithError("/firearms", t("deleteFailed", { error }), locale);

// src/lib/actions/firearms.ts:104 (updateFirearm)
if (error) redirectWithError("/firearms", t("deleteFailed", { error }), locale);

Impact

If creating a firearm fails, the user reads "the firearm could not be deleted". Confusing, and it makes a good bug report less likely.

Suggested direction

Add createFailed and updateFailed to actionError in messages/{es,en}.json and use them. updateFailed is already defined (used by matches/[id]/actions.ts:194), so adding createFailed is probably enough.

Found during a full code audit. One line per site.