ui: stop Run-now buttons wrapping to two lines

Three sites:
* Schedules list per-row Run-now / Edit / Delete column was 1fr
  next to a 1.3fr retention column — too narrow for the three
  buttons. Pin the action column to 240px and add
  whitespace-nowrap to each button so the layout can't squeeze
  them onto two lines regardless.
* Dashboard host_row Run-now button got whitespace-nowrap +
    for the same reason inside the 92px action column.
* Host detail header "Run backup now" —   the words so the
  button never breaks across lines if the header gets crowded.

Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>

web/templates/partials/host_row.html

@@ -63,10 +63,10 @@
               hx-swap="none"
               hx-disabled-elt="this">Retry</button>
     {{- else -}}
-      <button class="btn"
+      <button class="btn whitespace-nowrap"
               hx-post="/hosts/{{.ID}}/run-backup"
               hx-swap="none"
-              hx-disabled-elt="this">Run now</button>
+              hx-disabled-elt="this">Run&nbsp;now</button>
     {{- end -}}
   </div>
 </div>