Every lock of the store goes through Db::conn

Db::conn is documented as the one way to take the lock, yet five production and
test sites reached past it with db.0.lock(): the startup summary, the desktop's
trash sweep and config_get, and tests in sharing and update. All five now call
conn().

DRY pass #2, batch 2, F8 (#5372).

Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>

desktop/src-tauri/src/lib.rs

@@ -269,7 +269,7 @@ fn paint_window_before_the_webview_does(app: &tauri::App) {
 /// user is present for is one they can see the result of. A failure here is logged and
 /// stepped over — housekeeping must never be the reason the app won't open.
 fn sweep_local_trash(db: &local::Db) {
-    let conn = match db.0.lock() {
+    let conn = match db.conn() {
         Ok(conn) => conn,
         Err(_) => {
             log::warn!("skipping the trash sweep: store lock poisoned");