feat(book): redesign covers with 5 distinct publisher styles

- Style A (O'Reilly): EoS (owl), eBoot (fox), eDB (turtle), eHardware (eagle)
- Style B (Packt): eAI, eNI, EoStudio, eVera — bold gradients + geometric
- Style C (Manning): ebuild, eIPC, eBrowser — diagonal split, two-tone
- Style D (Apress): EoSim, eApps, eOffice — dark tech background
- Style E (Academic): eStocks, Ecosystem — clean minimal, serif title

Author: srpatcha