Fix settings dialog: increase height to show Save button

The settings dialog window height was too small (12 lines), causing the
footer to overlap with the 'Save' option at position 10. Users couldn't
see or select the Save button, preventing GPG key configuration from
being persisted.

Changes:
- Increased window height from 12 to 15 lines
- Adjusted y position to keep dialog centered
- Now all 4 options (GPG Signing, Select GPG Key, Save, Cancel) are
  fully visible with the footer below them

This was a pre-existing UI bug, not introduced by the restructuring.

trace/tui_app.py

@@ -2213,9 +2213,9 @@ class TUI:
         options = ["GPG Signing", "Select GPG Key", "Save", "Cancel"]
 
         curses.curs_set(0)
-        h = 12
+        h = 15  # Increased from 12 to properly show all 4 options + footer
         w = 60
-        y = self.height // 2 - 6
+        y = self.height // 2 - 7  # Adjusted to keep centered
         x = (self.width - w) // 2
 
         win = curses.newwin(h, w, y, x)