go.tools/dashboard: fix various small UI issues

- stop time column from wrapping,
- fix pagination on front page,
- left-align pagination buttons.

LGTM=dvyukov
R=dvyukov, golang-codereviews
CC=golang-codereviews
https://golang.org/cl/126410043

dashboard/app/build/ui.html

@@ -122,9 +122,11 @@
 
     {{with $.Pagination}}
     <div class="paginate">
+      <nav>
         <a {{if .HasPrev}}href="?{{with $.Package.Path}}repo={{.}}&{{end}}page={{.Prev}}"{{else}}class="inactive"{{end}}>newer</a>
         <a {{if .Next}}href="?{{with $.Package.Path}}repo={{.}}&{{end}}page={{.Next}}"{{else}}class="inactive"{{end}}>older</a>
         <a {{if .HasPrev}}href="."{{else}}class="inactive"{{end}}>latest</a>
+      </nav>
     </div>
     {{end}}
 

dashboard/app/static/style.css

@@ -186,7 +186,7 @@ table thead tr {
   font-size: 83%;
 }
 
-.build .desc, .build .date, .build .user {
+.build .desc, .build .time, .build .user {
   white-space: nowrap;
 }
  
@@ -205,7 +205,6 @@ table thead tr {
 /* pagination */
  
 .paginate nav {
-  text-align: center;
   padding: 0.5em;
   margin: 10px 0;
 }