Fix Stalwart startup to use stalwart.toml config

Stalwart was starting with --config config.json (RocksDB-only pointer)
instead of the full stalwart.toml configuration. This caused the HTTP
listener on port 8080 to not start, failing readiness probes.

Override container command to use stalwart.toml, which contains:
- HTTP listener on 0.0.0.0:8080 for web UI and healthz endpoints
- All email protocol listeners (SMTP 25, submission 587, IMAPS 993)
- TLS configuration

Fixes DEV-428 (503 no-available-server)
Related to DEV-422 (Stalwart not accessible)

Co-Authored-By: Paperclip <noreply@paperclip.ing>

apps/stalwart/stalwart-fresh-deployment.yaml

@@ -100,6 +100,7 @@ spec:
       containers:
       - name: stalwart
         image: stalwartlabs/stalwart:v0.16.11
+        command: ["/usr/local/bin/stalwart", "--config", "/etc/stalwart/stalwart.toml"]
         ports:
         - containerPort: 25
           name: smtp