feat(alerting): countExecutionsForAlerting for exchange-match evaluator

Adds AlertMatchSpec record (core) and ClickHouseSearchIndex.countExecutionsForAlerting —
no FINAL, no text subqueries. Filters by tenant, env, app, route, status, time window,
and optional after-cursor. Attributes (JSON string column) use inlined JSONExtractString
key literals since ClickHouse JDBC does not bind ? placeholders inside JSON functions.

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

cameleer-server-core/src/main/java/com/cameleer/server/core/alerting/AlertMatchSpec.java

@@ -0,0 +1,25 @@
+package com.cameleer.server.core.alerting;
+
+import java.time.Instant;
+import java.util.Map;
+
+/**
+ * Specification for alerting-specific execution counting.
+ * Distinct from {@code SearchRequest}: no text-in-body subqueries, no cursor, no {@code FINAL}.
+ * All fields except {@code tenantId}, {@code environment}, {@code from}, and {@code to} are nullable filters.
+ */
+public record AlertMatchSpec(
+        String tenantId,
+        String environment,
+        String applicationId,           // nullable — omit to match all apps
+        String routeId,                 // nullable — omit to match all routes
+        String status,                  // "FAILED" / "COMPLETED" / null for any
+        Map<String, String> attributes, // exact match on execution attribute key=value; empty = no filter
+        Instant from,
+        Instant to,
+        Instant after                   // nullable; used by PER_EXCHANGE mode to advance cursor past last seen
+) {
+    public AlertMatchSpec {
+        attributes = attributes == null ? Map.of() : Map.copyOf(attributes);
+    }
+}