Add unattended end-to-end self-test mode for the production webview

VOICED_SELFTEST_OUT runs the Diagnostics checks plus an issue, archive,
export (searchable, flattened, re-render), cancel and archive-immutability
flow through the real IPC, writes a JSON report and exits. Inert without
the variable; doubles as the per-release gate on installed builds.

src-tauri/src/lib.rs

@@ -2,6 +2,7 @@ mod commands;
 mod db;
 mod gst;
 mod models;
+mod selftest;
 
 use rusqlite::Connection;
 use std::path::{Path, PathBuf};
@@ -135,6 +136,8 @@ pub fn run() {
             commands::files::get_last_export_dir,
             commands::files::reveal_in_folder,
             commands::files::open_file,
+            selftest::selftest_config,
+            selftest::selftest_report,
         ])
         .run(tauri::generate_context!());