fix: scope pg_stat_activity queries by ApplicationName for tenant isolation

DatabaseAdminController's active-queries and kill-query endpoints could
expose SQL text from other tenants sharing the same PostgreSQL instance.
Added ApplicationName=tenant_{id} to the JDBC URL and filter
pg_stat_activity by application_name so each tenant only sees its own
connections.

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

cameleer3-server-app/src/main/resources/application.yml

@@ -7,7 +7,7 @@ spring:
       max-file-size: 200MB
       max-request-size: 200MB
   datasource:
-    url: ${SPRING_DATASOURCE_URL:jdbc:postgresql://localhost:5432/cameleer3?currentSchema=tenant_${cameleer.server.tenant.id}}
+    url: ${SPRING_DATASOURCE_URL:jdbc:postgresql://localhost:5432/cameleer3?currentSchema=tenant_${cameleer.server.tenant.id}&ApplicationName=tenant_${cameleer.server.tenant.id}}
     username: ${SPRING_DATASOURCE_USERNAME:cameleer}
     password: ${SPRING_DATASOURCE_PASSWORD:cameleer_dev}
     driver-class-name: org.postgresql.Driver