fix(deploy): stop previous active deployment before START_REPLICAS (fixes 409)

Container names are deterministic: {tenant}-{envSlug}-{appSlug}-{replica}.
The prior code did the stop-existing step at SWAP_TRAFFIC, *after*
START_REPLICAS had already tried to create containers with the same
names — so a redeploy against a RUNNING app consistently failed with
Docker 409 "container name already in use".

Move the stop-existing block to run right after CREATE_NETWORK and
before START_REPLICAS. SWAP_TRAFFIC becomes a label-only marker (traffic
is swapped implicitly by Traefik labels once new replicas are healthy).

Also: add `findActiveByAppIdAndEnvironmentIdExcluding` so the SQL
excludes the current deployment by id — previously the Java-side
`!id.equals(me)` guard failed because the newly-inserted row has
status=STARTING (DB default) and ORDER BY created_at DESC LIMIT 1
picked the new row, hiding the actual previous deployment.

Trade-off: this is destroy-then-start rather than true blue/green —
brief downtime during the swap. Matches the pre-unified-page behavior
and is what users reasonably expect. True blue/green would require
per-deployment container names.

Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>

cameleer-server-app/src/main/java/com/cameleer/server/app/runtime/DeploymentExecutor.java

@@ -167,6 +167,21 @@ public class DeploymentExecutor {
                 }
             }
 
+            // === STOP PREVIOUS ACTIVE DEPLOYMENT ===
+            // Container names are deterministic ({tenant}-{env}-{app}-{replica}), so a
+            // previous active deployment holds the Docker names we need. Stop + remove
+            // it before starting new replicas to avoid a 409 name conflict. Excluding
+            // the current deployment id by SQL (not Java) because the newly created
+            // row already has status=STARTING and would otherwise be picked by
+            // findActiveByAppIdAndEnvironmentId ORDER BY created_at DESC LIMIT 1.
+            Optional<Deployment> previous = deploymentRepository.findActiveByAppIdAndEnvironmentIdExcluding(
+                    deployment.appId(), deployment.environmentId(), deployment.id());
+            if (previous.isPresent()) {
+                log.info("Stopping previous deployment {} before starting new replicas", previous.get().id());
+                stopDeploymentContainers(previous.get());
+                deploymentService.markStopped(previous.get().id());
+            }
+
             // === START REPLICAS ===
             updateStage(deployment.id(), DeployStage.START_REPLICAS);
 
@@ -244,16 +259,12 @@ public class DeploymentExecutor {
             pgDeployRepo.updateReplicaStates(deployment.id(), replicaStates);
 
             // === SWAP TRAFFIC ===
+            // Traffic is routed via Traefik Docker labels, so the "swap" happens
+            // implicitly once the new replicas are healthy and the old containers
+            // are gone. The old deployment was already stopped before START_REPLICAS
+            // to free the deterministic container names.
             updateStage(deployment.id(), DeployStage.SWAP_TRAFFIC);
 
-            Optional<Deployment> existing = deploymentRepository.findActiveByAppIdAndEnvironmentId(
-                    deployment.appId(), deployment.environmentId());
-            if (existing.isPresent() && !existing.get().id().equals(deployment.id())) {
-                stopDeploymentContainers(existing.get());
-                deploymentService.markStopped(existing.get().id());
-                log.info("Stopped previous deployment {} for replacement", existing.get().id());
-            }
-
             // === COMPLETE ===
             updateStage(deployment.id(), DeployStage.COMPLETE);
 

cameleer-server-app/src/main/java/com/cameleer/server/app/storage/PostgresDeploymentRepository.java

@@ -63,6 +63,16 @@ public class PostgresDeploymentRepository implements DeploymentRepository {
         return results.isEmpty() ? Optional.empty() : Optional.of(results.get(0));
     }
 
+    @Override
+    public Optional<Deployment> findActiveByAppIdAndEnvironmentIdExcluding(UUID appId, UUID environmentId, UUID excludeDeploymentId) {
+        var results = jdbc.query(
+                "SELECT " + SELECT_COLS + " FROM deployments WHERE app_id = ? AND environment_id = ? " +
+                "AND status IN ('STARTING', 'RUNNING', 'DEGRADED') AND id <> ? " +
+                "ORDER BY created_at DESC LIMIT 1",
+                (rs, rowNum) -> mapRow(rs), appId, environmentId, excludeDeploymentId);
+        return results.isEmpty() ? Optional.empty() : Optional.of(results.get(0));
+    }
+
     public List<Deployment> findByStatus(List<DeploymentStatus> statuses) {
         String placeholders = String.join(",", statuses.stream().map(s -> "'" + s.name() + "'").toList());
         return jdbc.query(

cameleer-server-core/src/main/java/com/cameleer/server/core/runtime/DeploymentRepository.java

@@ -9,6 +9,7 @@ public interface DeploymentRepository {
     List<Deployment> findByEnvironmentId(UUID environmentId);
     Optional<Deployment> findById(UUID id);
     Optional<Deployment> findActiveByAppIdAndEnvironmentId(UUID appId, UUID environmentId);
+    Optional<Deployment> findActiveByAppIdAndEnvironmentIdExcluding(UUID appId, UUID environmentId, UUID excludeDeploymentId);
     UUID create(UUID appId, UUID appVersionId, UUID environmentId, String containerName);
     void updateStatus(UUID id, DeploymentStatus status, String containerId, String errorMessage);
     void markDeployed(UUID id);