feat: mark-spam, rule priority persistence, run-rules-on-selected, icons fix, scheduled send + reader polish

- Mark as spam: moves mail to Spam/Junk folder of account
- Rule priority: persistPriorityOrder persists 1..N via RuleDao::update
- Run rules on selected: uses MailListView::selectedMailIds() + onRunRulesOnSelected
- Icons: switch code to qrc short aliases (close/send/bold/etc) + new detach.svg
  -> resolves all 'Cannot open file' SVG warnings at startup
- Categories: CompactMailDelegate paints category chips from CategoryDao
- Scheduled send: MailService::scheduleSend with QTimer; wire both composer paths
- Reader: show real 'Para:' recipient; delete attachment removes stored file

icons.qrc

@@ -12,6 +12,7 @@
         <file alias="reply.svg">resources/icons/SVG/Linear/Arrows Action/Reply.svg</file>
         <file alias="forward.svg">resources/icons/SVG/Linear/Arrows Action/Forward.svg</file>
         <file alias="trash.svg">resources/icons/SVG/Linear/Essentional, UI/Trash Bin Minimalistic.svg</file>
+        <file alias="detach.svg">resources/icons/SVG/Linear/Arrows Action/Square Top Down.svg</file>
         <file alias="filter.svg">resources/icons/SVG/Linear/Design, Tools/Filters.svg</file>
         <file alias="play.svg">resources/icons/SVG/Linear/Time/Stopwatch Play.svg</file>
         <file alias="file-text.svg">resources/icons/SVG/Linear/Files/File Text.svg</file>