feat: GTK3-only theming overhaul—new theme service (discover/import/inherits), layered CSS+settings.ini apply w/ safe rollback + caching; widget/xtext palette mapping + all-colors editor; lots of win32/CI libarchive plumbing + installer assets;

src/common/gtk3-theme-service.h

@@ -0,0 +1,32 @@
+#ifndef ZOITECHAT_GTK3_THEME_SERVICE_H
+#define ZOITECHAT_GTK3_THEME_SERVICE_H
+
+#include <glib.h>
+
+typedef enum
+{
+	ZOITECHAT_GTK3_THEME_SOURCE_SYSTEM = 0,
+	ZOITECHAT_GTK3_THEME_SOURCE_USER = 1
+} ZoitechatGtk3ThemeSource;
+
+typedef struct
+{
+	char *id;
+	char *display_name;
+	char *path;
+	gboolean has_dark_variant;
+	char *thumbnail_path;
+	ZoitechatGtk3ThemeSource source;
+} ZoitechatGtk3Theme;
+
+char *zoitechat_gtk3_theme_service_get_user_themes_dir (void);
+GPtrArray *zoitechat_gtk3_theme_service_discover (void);
+void zoitechat_gtk3_theme_free (ZoitechatGtk3Theme *theme);
+ZoitechatGtk3Theme *zoitechat_gtk3_theme_find_by_id (const char *theme_id);
+gboolean zoitechat_gtk3_theme_service_import (const char *source_path, char **imported_id, GError **error);
+gboolean zoitechat_gtk3_theme_service_remove_user_theme (const char *theme_id, GError **error);
+char *zoitechat_gtk3_theme_pick_css_dir_for_minor (const char *theme_root, int preferred_minor);
+char *zoitechat_gtk3_theme_pick_css_dir (const char *theme_root);
+GPtrArray *zoitechat_gtk3_theme_build_inheritance_chain (const char *theme_root);
+
+#endif