Fix status filter OR logic and add P99/active stats endpoint

Status filter now parses comma-separated values into SQL IN clause
instead of exact match, so filtering by multiple statuses works.

Added GET /api/v1/search/stats returning P99 latency (last hour) and
active execution count, wired into the UI stat cards with 10s polling.

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

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

@@ -1,5 +1,6 @@
 package com.cameleer3.server.app.controller;
 
+import com.cameleer3.server.core.search.ExecutionStats;
 import com.cameleer3.server.core.search.ExecutionSummary;
 import com.cameleer3.server.core.search.SearchRequest;
 import com.cameleer3.server.core.search.SearchResult;
@@ -65,4 +66,10 @@ public class SearchController {
             @RequestBody SearchRequest request) {
         return ResponseEntity.ok(searchService.search(request));
     }
+
+    @GetMapping("/stats")
+    @Operation(summary = "Aggregate execution stats (P99 latency, active count)")
+    public ResponseEntity<ExecutionStats> stats() {
+        return ResponseEntity.ok(searchService.stats());
+    }
 }