Add route diagram page with execution overlay and group-aware APIs

Backend: Add group filtering to agent list, search, stats, and timeseries
endpoints. Add diagram lookup by group+routeId. Resolve application group
to agent IDs server-side for ClickHouse IN-clause queries.

Frontend: New route detail page at /apps/{group}/routes/{routeId} with
three tabs (Diagram, Performance, Processor Tree). SVG diagram rendering
with panzoom, execution overlay (glow effects, duration/sequence badges,
flow particles, minimap), and processor detail panel. uPlot charts for
performance tab replacing old SVG sparklines. Ctrl+Click from
ExecutionExplorer navigates to route diagram with overlay.

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

ui/src/api/queries/diagrams.ts

@@ -0,0 +1,31 @@
+import { useQuery } from '@tanstack/react-query';
+import { api } from '../client';
+
+export function useDiagramLayout(contentHash: string | null) {
+  return useQuery({
+    queryKey: ['diagrams', 'layout', contentHash],
+    queryFn: async () => {
+      const { data, error } = await api.GET('/diagrams/{contentHash}/render', {
+        params: { path: { contentHash: contentHash! } },
+        headers: { Accept: 'application/json' },
+      });
+      if (error) throw new Error('Failed to load diagram layout');
+      return data!;
+    },
+    enabled: !!contentHash,
+  });
+}
+
+export function useDiagramByRoute(group: string | undefined, routeId: string | undefined) {
+  return useQuery({
+    queryKey: ['diagrams', 'byRoute', group, routeId],
+    queryFn: async () => {
+      const { data, error } = await api.GET('/diagrams', {
+        params: { query: { group: group!, routeId: routeId! } },
+      });
+      if (error) throw new Error('Failed to load diagram for route');
+      return data!;
+    },
+    enabled: !!group && !!routeId,
+  });
+}