feat: add review status icon and merge status indicator to PR list rows

Add per-PR review state aggregation by fetching reviews concurrently
via the existing semaphore pattern. Display review status (approved,
changes requested, awaiting) and merge status (ready/conflicts) as
compact badges in each PR card row.

- Add ReviewState field to PullRequest struct
- Add GetPullReviewState() and EnrichPullsWithReviewState() to client
- Call enrichment in ListPulls handler after fetching PRs
- Update pulls template with review and merge badges
- Add CSS for .review-badge and .merge-badge classes

Closes leeworks-agents/gitea-mobile#97

Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>

internal/templates/pulls.html

@@ -12,7 +12,13 @@
       {{end}}
       <span class="diff-add">+{{.Additions}}</span>
       <span class="diff-del">-{{.Deletions}}</span>
-      {{if .Mergeable}}<span style="color:var(--accent-green);font-size:0.7rem;">mergeable</span>{{end}}
+      {{if eq .ReviewState "approved"}}<span class="review-badge review-approved" title="Approved">&#10003;</span>
+      {{else if eq .ReviewState "changes_requested"}}<span class="review-badge review-changes" title="Changes requested">&#10007;</span>
+      {{else if eq .ReviewState "pending"}}<span class="review-badge review-pending" title="Awaiting review">&#9202;</span>
+      {{end}}
+      {{if .Mergeable}}<span class="merge-badge merge-ready" title="Ready to merge">&#9654; Ready</span>
+      {{else}}<span class="merge-badge merge-conflicts" title="Has conflicts or not mergeable">Conflicts</span>
+      {{end}}
     </div>
   </div>
   {{end}}