feat: add environment filtering across all APIs and UI

Backend: Added optional `environment` query parameter to catalog,
search, stats, timeseries, punchcard, top-errors, logs, and agents
endpoints. ClickHouse queries filter by environment when specified
(literal SQL for AggregatingMergeTree, ? binds for raw tables).
StatsStore interface methods all accept environment parameter.

UI: Added EnvironmentSelector component (compact native select).
LayoutShell extracts distinct environments from agent data and
passes selected environment to catalog and agent queries via URL
search param (?env=). TopBar shows current environment label.

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

ui/src/api/queries/executions.ts

@@ -8,10 +8,11 @@ export function useExecutionStats(
   timeTo: string | undefined,
   routeId?: string,
   application?: string,
+  environment?: string,
 ) {
   const live = useLiveQuery(10_000);
   return useQuery({
-    queryKey: ['executions', 'stats', timeFrom, timeTo, routeId, application],
+    queryKey: ['executions', 'stats', timeFrom, timeTo, routeId, application, environment],
     queryFn: async () => {
       const { data, error } = await api.GET('/search/stats', {
         params: {
@@ -20,6 +21,7 @@ export function useExecutionStats(
             to: timeTo || undefined,
             routeId: routeId || undefined,
             application: application || undefined,
+            environment: environment || undefined,
           },
         },
       });
@@ -70,10 +72,11 @@ export function useStatsTimeseries(
   timeTo: string | undefined,
   routeId?: string,
   application?: string,
+  environment?: string,
 ) {
   const live = useLiveQuery(30_000);
   return useQuery({
-    queryKey: ['executions', 'timeseries', timeFrom, timeTo, routeId, application],
+    queryKey: ['executions', 'timeseries', timeFrom, timeTo, routeId, application, environment],
     queryFn: async () => {
       const { data, error } = await api.GET('/search/stats/timeseries', {
         params: {
@@ -83,6 +86,7 @@ export function useStatsTimeseries(
             buckets: 24,
             routeId: routeId || undefined,
             application: application || undefined,
+            environment: environment || undefined,
           },
         },
       });