feat(config): add the trash query generator

Adds trash as a fifth built-in query filter beside Unread, Inbox,
Important and Sent, composing per-account exactly as Sent does:
Config::resolvedQuery() asks each account for its own trashQuery()
rather than wrapping the all-accounts union, and an account with no
trash folder resolves to matchNothingQuery() rather than "match
everything".

Also gives the Trash button a toolbar icon (user-trash) and a trash
key to the mainwindow fixture that asserts every filter button carries
one; without it the button is skipped from the row entirely (no
account configured a trash folder), and the existing icon test found
no button to check.

1 files changed, 7 insertions, 0 deletions

diff --git a/src/config.h b/src/config.h
index 1feeeda..f60e7cc 100644
--- a/src/config.h
+++ b/src/config.h
@@ -291,6 +291,13 @@ public:
     /// open-coded at the call site.
     QString allSentQuery() const;
 
+    /// Matches every configured account's trash, or empty when none has one.
+    ///
+    /// Joins only the NON-EMPTY trashQuery() results, for the same reason
+    /// allSentQuery() does: notmuch accepts a bare "or" without complaint and
+    /// silently answers a different question.
+    QString allTrashQuery() const;
+
     /// Matches every configured account's drafts, or empty when none has one.
     ///
     /// Joins only the NON-EMPTY draftsQuery() results, for the same reason