Add a get_doc_handle virtual method to EvDocumentClass so the view layer
can obtain the underlying GepubDoc without depending on backend types
directly. This prepares for replacing EvWebView with GepubWidget which
needs the GepubDoc to render content.

Assisted-by: OpenCode:claude-opus-4-6

Remove the bundled minizip directory, unused includes, and the night
mode virtual methods from EvDocumentClass which are no longer called by
any code. Night mode is now handled entirely through WebKit user
stylesheets.

Assisted-by: OpenCode:claude-opus-4-6

Replace the hand-rolled EPUB parsing with libgepub. This removes the
bundled minizip library, custom XML utilities, and temporary directory
extraction in favor of GepubDoc which handles archive access, metadata,
spine navigation, and table of contents. An epub:// URI scheme handler
serves resources directly from the archive without extracting to disk.
Search and night mode are stubbed as no-ops pending follow-up commits.

Assisted-by: OpenCode:claude-opus-4-6

Not everyone who reads PDF's is necessarily a LaTeX user.
These changes allow users to install atril without the huge bagage
of tex-live on systems where synctex isn't provided as a stand alone
library.

  $ cd cut-n-paste/synctex
  $ rm synctex_*
  $ ./update-synctex-from-TL.sh

Test on Fedora:

  1. Install required packages
     $ sudo dnf install texlive-scheme-basic texlive-lipsum -y

  2. Build a pdf with synctex enabled
     $ cat <<EOF >> file.tex
\documentclass[12pt]{report}
\usepackage{lipsum}
\begin{document}
\chapter{Introduction}
\lipsum[2-4]
\end{document}
EOF
     $ pdflatex -synctex=1 file.tex

   3. Open file.pdf using atril

   4. Search any text string