Add live badge to issues with active runs on /issues/active

Server: the /companies/:companyId/live-runs endpoint now returns
issueId extracted from contextSnapshot, so the UI can match runs
to issues without N+1 queries.

UI (Issues.tsx): fetches company live runs (with 5s polling), builds
a set of issue IDs with active runs, and shows a pulsing "Live" badge
in each matching issue row — matching the existing blue live indicator
style from AgentDetail.

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

ui/src/api/heartbeats.ts

@@ -18,6 +18,7 @@ export interface LiveRunForIssue {
   agentId: string;
   agentName: string;
   adapterType: string;
+  issueId?: string | null;
 }
 
 export const heartbeatsApi = {