docs: improve custom-strings flag description

Change "custom UI strings" to "custom translations" to better reflect that this feature uses the i18n system and could be used for more than just UI elements, making it more accurate and future-proof.

🤖 Generated with [Claude Code](https://claude.ai/code)

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

Author: strickvl

src/node/cli.ts

@@ -300,7 +300,7 @@ export const options: Options<Required<UserProvidedArgs>> = {
   },
   "custom-strings": {
     type: "string",
-    description: "Path to JSON file or raw JSON string with custom UI strings. Merges with default strings and supports all i18n keys.",
+    description: "Path to JSON file or raw JSON string with custom translations. Merges with default strings and supports all i18n keys.",
   },
 }