refactor(frontend): deduplicate CSS keyframes, unify types, extract format utils, add UI states, trim mock data

- Remove duplicate @keyframes pulse-* from 3 component files (already in nexus-tokens.css)
- Rename AgentDetail → AgentDetailData in dashboard types to avoid collision with types/agent.ts
- Extract shared formatNumber/initials/formatTime to utils/format.ts
- Simplify FlowBoard: use agentStore modal/selection getters instead of duplicating local state
- Add error banner + empty state to IrisChat; add loading skeleton + error/empty states to TaskStrip
- Remove 105-line unused mockAgents array from useFlowLayout
- Reduce operations store fallbacks from hardcoded preview data to minimal safe defaults
- Update operations store tests to match lean fallback structure
- Net: -73 lines, cleaner imports, fewer magic strings

frontend/src/utils/format.ts

@@ -0,0 +1,30 @@
+/**
+ * Shared formatting utilities for Nexus Dashboard
+ */
+
+/** Format a number with SI suffixes (k, M) */
+export function formatNumber(n: number): string {
+  if (n >= 1_000_000) return (n / 1_000_000).toFixed(1) + 'M'
+  if (n >= 1_000) return (n / 1_000).toFixed(1) + 'k'
+  return String(n)
+}
+
+/** Format currency with $ prefix */
+export function formatCurrency(n: number): string {
+  return '$' + n.toFixed(2)
+}
+
+/** Format a Date as German locale time HH:MM:SS */
+export function formatTime(d: Date): string {
+  return d.toLocaleTimeString('de-DE', { hour: '2-digit', minute: '2-digit', second: '2-digit' })
+}
+
+/** Format a Date as German locale time HH:MM */
+export function formatTimeShort(d: Date): string {
+  return d.toLocaleTimeString('de-DE', { hour: '2-digit', minute: '2-digit' })
+}
+
+/** Extract initials (max 2 chars) from a display name */
+export function initials(name: string): string {
+  return name.split(' ').map(p => p[0]).join('').slice(0, 2).toUpperCase()
+}