epub: Replace backend internals with libgepub

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

2 files changed, 34 insertions, 1 deletions

diff --git a/libdocument/ev-document.c b/libdocument/ev-document.c
index 96b80946..74efc1d4 100644
--- a/libdocument/ev-document.c
+++ b/libdocument/ev-document.c
@@ -942,6 +942,30 @@ ev_rect_cmp (EvRectangle *a,
 		  (ABS (a->y2 - b->y2) < EPSILON));
 }
 
+GBytes *
+ev_document_get_resource (EvDocument  *document,
+                          const gchar *path)
+{
+	EvDocumentClass *klass = EV_DOCUMENT_GET_CLASS (document);
+
+	if (klass->get_resource)
+		return klass->get_resource (document, path);
+
+	return NULL;
+}
+
+gchar *
+ev_document_get_resource_mime (EvDocument  *document,
+                               const gchar *path)
+{
+	EvDocumentClass *klass = EV_DOCUMENT_GET_CLASS (document);
+
+	if (klass->get_resource_mime)
+		return klass->get_resource_mime (document, path);
+
+	return NULL;
+}
+
 void
 ev_document_toggle_night_mode(EvDocument *document,gboolean night)
 {
diff --git a/libdocument/ev-document.h b/libdocument/ev-document.h
index ea0016c0..6a73d0f1 100644
--- a/libdocument/ev-document.h
+++ b/libdocument/ev-document.h
@@ -118,6 +118,11 @@ struct _EvDocumentClass
 
 	void              (* toggle_night_mode)  (EvDocument      *document,gboolean night);
 	void              (*check_add_night_sheet)(EvDocument      *document);
+
+	GBytes          * (* get_resource)       (EvDocument      *document,
+	                                          const gchar     *path);
+	gchar           * (* get_resource_mime)  (EvDocument      *document,
+	                                          const gchar     *path);
 };
 
 GType            ev_document_get_type             (void) G_GNUC_CONST;
@@ -185,7 +190,11 @@ EvMapping       *ev_document_synctex_forward_search
 gint             ev_rect_cmp                      (EvRectangle     *a,
 					           EvRectangle     *b);
 void            ev_document_toggle_night_mode     (EvDocument *document,gboolean night);
-void			ev_document_check_add_night_sheet (EvDocument *document);
+void            ev_document_check_add_night_sheet (EvDocument *document);
+GBytes         *ev_document_get_resource          (EvDocument      *document,
+                                                   const gchar     *path);
+gchar          *ev_document_get_resource_mime     (EvDocument      *document,
+                                                   const gchar     *path);
 
 #define EV_TYPE_RECTANGLE (ev_rectangle_get_type ())
 struct _EvRectangle