chore(coturn): automated TURN shared-secret rotation

Scheduled rotation (Issue #38). New secret generated, re-encrypted with
the scoped rotation age key, checksum/rotated-at annotations bumped so
Flux restarts coturn + synapse-main on merge. Please review and merge.

apps/production/kustomization.yaml

@@ -16,7 +16,7 @@ patches:
         value: "401f8a87d0ef5d91d2e5032d4aede42c"
       - op: add
         path: /metadata/annotations/turn-secret-checksum
-        value: "9b0383df36943da3b32198b6bd32bfcd"
+        value: "d220c0e4ff8f7106328c8827d47e8734"
 
 resources:
   - matrix-postgres-auth.yaml
@@ -42,4 +42,4 @@ resources:
   - synapse-backup.yaml
   # Automatisierte TURN-Secret-Rotation (Issue #38)
   - turn-secret-rotation-secret.yaml
-  - turn-secret-rotation.yaml
+  - turn-secret-rotation.yaml