fix(alerting): use ALTER TABLE MODIFY SETTING to enable projections on executions ReplacingMergeTree

Investigated three approaches for CH 24.12:
- Inline SETTINGS on ADD PROJECTION: rejected (UNKNOWN_SETTING — not a query-level setting).
- ALTER TABLE MODIFY SETTING deduplicate_merge_projection_mode='rebuild': works; persists in
  table metadata across connection restarts; runs before ADD PROJECTION in the SQL script.
- Session-level JDBC URL param: not pursued (MODIFY SETTING is strictly better).

alerting_projections.sql now runs MODIFY SETTING before the two executions ADD PROJECTIONs.
AlertingProjectionsIT strengthened to assert all four projections (including alerting_app_status
and alerting_route_status on executions) exist after schema init.

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

cameleer-server-app/src/test/java/com/cameleer/server/app/search/AlertingProjectionsIT.java

@@ -34,17 +34,19 @@ class AlertingProjectionsIT {
     }
 
     @Test
-    void mergeTreeProjectionsExistAfterInit() {
-        // logs and agent_metrics are plain MergeTree — projections always succeed.
-        // executions is ReplacingMergeTree; its projections require the session setting
-        // deduplicate_merge_projection_mode='rebuild' which is unavailable via JDBC pool,
-        // so they are best-effort and not asserted here.
+    void allFourProjectionsExistAfterInit() {
+        // logs and agent_metrics are plain MergeTree — always succeed.
+        // executions is ReplacingMergeTree; its projections now succeed because
+        // alerting_projections.sql runs ALTER TABLE executions MODIFY SETTING
+        // deduplicate_merge_projection_mode='rebuild' before the ADD PROJECTION statements.
         List<String> names = jdbc.queryForList(
-                "SELECT name FROM system.projections WHERE table IN ('logs', 'agent_metrics')",
+                "SELECT name FROM system.projections WHERE table IN ('logs', 'agent_metrics', 'executions')",
                 String.class);
 
-        assertThat(names).contains(
+        assertThat(names).containsExactlyInAnyOrder(
                 "alerting_app_level",
-                "alerting_instance_metric");
+                "alerting_instance_metric",
+                "alerting_app_status",
+                "alerting_route_status");
     }
 }