Wrap the top bar's buttons onto a second row when narrow (closes #272)

The top bar's two sides were held apart only by justify-between, with
no gap and no wrapping, so at 390 px "by @sneak" ended where the New
App button began. The bar's row now wraps and has a gap: in a window
too narrow for one row, New App and Logout move to a second row; on
wider windows the bar looks as before.

Model: opus-5-5

TODO.md

@@ -20,6 +20,10 @@ regress.
 
 # Completed Steps
 
+- 2026-10-02: In a window too narrow for the top bar, such as 390 px, the New
+  App and Logout buttons move to a second row instead of running into "by
+  @sneak"; the bar keeps a gap between its two sides at every width (#272).
+
 - 2026-10-02: App names may contain dots, such as `sneak.berlin`: lowercase
   letters and numbers joined by single dots or by hyphens, 2 to 63 characters.
   Docker accepts every such name in the image name `upaas-<name>`; a dot needs a