Make username/password connect prompts hard to miss (issue #22)

The inline prompt bar previously had no explicit styling and rendered
in the same color as the rest of the tab; a tab showing the prompt in
the background had no indication anything needed attention. The bar
now uses a solid QPalette::Highlight fill with HighlightedText for the
label and a hand-drawn contrasting badge, and a background tab gets a
"(Needs input)" title suffix plus a distinct tab-bar color.

A first pass at the tab color (#6a1b9a) was reported unreadable in
dark mode; replaced with #ab47bc, tuned to match the visibility of the
existing connection-state colors.

Bump version to v2026.9.16.6.

Co-Authored-By: Claude Sonnet 5 <noreply@anthropic.com>

src/session_window.h

@@ -4,6 +4,7 @@
 #include "profile_repository.h"
 #include "session_tab.h"
 
+#include <QHash>
 #include <QMainWindow>
 
 class QTabWidget;
@@ -21,6 +22,10 @@ private:
     QTabWidget* m_tabs;
     ProfilesWindow* m_profilesWidget;
     SessionUiPreferences m_preferences;
+    // Last known connection state per tab, so the tab color can be
+    // restored correctly once an awaitingUserInputChanged(false) fires
+    // (that signal is orthogonal to SessionState -- see session_tab.h).
+    QHash<SessionTab*, SessionState> m_tabStates;
 
     void addSessionTab(const Profile& profile);
     void updateTabTitle(SessionTab* tab, const QString& title);