feat(campaigns): campaign timing panel with Red/Blue aggregated metrics

Backend: GET /campaigns/{id}/timing-summary
  Aggregates timing across all campaign tests:
  - red_execution_secs: red_started_at → blue_started_at (minus paused)
  - blue_queue_secs:    blue_started_at → blue_work_started_at
  - blue_evaluation_secs: blue_work_started_at → validated (minus paused)
  - total_secs: sum of all three phases
  Returns totals + per-test breakdown sorted by total time desc.

Frontend: new CampaignTimingPanel component replaces WorklogTimeline
  - 4 summary cards: Red Execution / Blue Queue / Blue Evaluation / Total
  - Stacked horizontal bar showing time distribution
  - Per-test breakdown with individual mini-bars and phase durations
  - Shows 'No tests started yet' when no timing data available

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

frontend/src/pages/CampaignDetailPage.tsx

@@ -31,7 +31,7 @@ import {
 import { useAuth } from "../context/AuthContext";
 import CampaignTimeline from "../components/CampaignTimeline";
 import JiraLinkPanel from "../components/JiraLinkPanel";
-import WorklogTimeline from "../components/WorklogTimeline";
+import CampaignTimingPanel from "../components/CampaignTimingPanel";
 import AddTestToCampaignModal from "../components/AddTestToCampaignModal";
 
 const statusColors: Record<string, string> = {
@@ -629,10 +629,10 @@ export default function CampaignDetailPage() {
         )}
       </div>
 
-      {/* Jira & Worklogs — read-only, automatically managed */}
+      {/* Jira + Campaign Timing */}
       <div className="grid gap-6 lg:grid-cols-2">
         <JiraLinkPanel entityType="campaign" entityId={campaignId!} readOnly label={campaign.name} />
-        <WorklogTimeline entityType="campaign" entityId={campaignId!} readOnly />
+        <CampaignTimingPanel campaignId={campaignId!} />
       </div>
 
       {/* Add Test to Campaign Modal */}