Does al-Kafi (1/409) state that the Imams have complete authority over everything in the heavens and earth, despite the Quran attributing these qualities solely to Allah? What does the divinity of Imamate signify?
An English translation of this is (alongside the Arabic text) is available here:
Chapter 105 (page 66-74 of the PDF)
https://www.wofis.com/book/18-AL-KAFI%20The%20Book%20of%20Divine%20Proof...(II)
This edition notes some weaknesses and problems with the hadith in this chapter.
In any case, Shi'a have varying views about the spiritual nature, knowledge, and authority of the Imams. Some take a rather expansive view, and some take a more restrictive view.
As for the more expansive view, you could read through the book by Mohammad Ali Amir-Moezzi The Divine Guide in Early Shi'ism, which attempts to explain what this means. This tends to be a love-or-hate book - some people love it, other people hate it - but it handles the subject excellently.
Ultimately, if you are Shi'i, this is a theological issue you will have to decide on for yourself (and your views may change over time). If you are not Shi'i, you can still explore and appreciate the variety of views.