Restore Stalwart bootstrap ConfigMap (non-destructive recovery)

CONTEXT: DEV-403 - Stalwart pod not starting after ConfigMap revert

ROOT CAUSE:
- The stalwart-bootstrap-config ConfigMap was manually created on July 5
- It was added to GitOps at commit 191614f (12:27 today)
- It was reverted at commit fcc5042 (12:56 today)
- ArgoCD pruned the ConfigMap from the cluster after the revert
- Stalwart deployment requires this ConfigMap to start

RECOVERY:
This commit restores the ConfigMap to Git so ArgoCD can recreate it.
The ConfigMap content is identical to the working version from before.
This is a non-destructive recovery - no data or accounts are affected.

The actual Stalwart data on PVC stalwart-data remains intact.

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

apps/stalwart/stalwart-bootstrap-config.yaml

@@ -0,0 +1,8 @@
+---
+apiVersion: v1
+kind: ConfigMap
+metadata:
+  name: stalwart-bootstrap-config
+  namespace: stalwart
+data:
+  config.json: '{"@type":"RocksDb","path":"/var/lib/stalwart"}'