Make stats endpoint respect selected time window instead of hardcoded last hour

P99 latency and active count now use the same from/to parameters as the
timeseries sparklines, so all stat cards are consistent with the user's
selected time range.

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

cameleer3-server-app/src/main/java/com/cameleer3/server/app/controller/SearchController.java

@@ -70,8 +70,11 @@ public class SearchController {
 
     @GetMapping("/stats")
     @Operation(summary = "Aggregate execution stats (P99 latency, active count)")
-    public ResponseEntity<ExecutionStats> stats() {
-        return ResponseEntity.ok(searchService.stats());
+    public ResponseEntity<ExecutionStats> stats(
+            @RequestParam Instant from,
+            @RequestParam(required = false) Instant to) {
+        Instant end = to != null ? to : Instant.now();
+        return ResponseEntity.ok(searchService.stats(from, end));
     }
 
     @GetMapping("/stats/timeseries")

cameleer3-server-app/src/main/java/com/cameleer3/server/app/search/ClickHouseSearchEngine.java

@@ -88,11 +88,11 @@ public class ClickHouseSearchEngine implements SearchEngine {
     }
 
     @Override
-    public ExecutionStats stats() {
+    public ExecutionStats stats(Instant from, Instant to) {
         Long p99 = jdbcTemplate.queryForObject(
                 "SELECT quantile(0.99)(duration_ms) FROM route_executions " +
-                "WHERE start_time >= now() - INTERVAL 1 HOUR",
-                Long.class);
+                "WHERE start_time >= ? AND start_time <= ?",
+                Long.class, Timestamp.from(from), Timestamp.from(to));
         Long active = jdbcTemplate.queryForObject(
                 "SELECT count() FROM route_executions WHERE status = 'RUNNING'",
                 Long.class);