feat(connections): Add Ingress with TLS and reorganize to applications/signal-cli

- Move manifests from cluster/platform/connections to cluster/applications/signal-cli
- Add Ingress for connections.local.mk-labs.cloud with cert-manager TLS
- Update ArgoCD application path to cluster/applications/signal-cli
- Configure letsencrypt-prod cluster issuer for automatic TLS certificates

This enables external HTTPS access to the Signal CLI REST API for Hermes
notifications with automatic certificate management.

cluster/applications/signal-cli/ingress.yaml

@@ -0,0 +1,29 @@
+apiVersion: networking.k8s.io/v1
+kind: Ingress
+metadata:
+  name: connections
+  namespace: connections
+  labels:
+    app.kubernetes.io/name: connections
+    app.kubernetes.io/component: messaging-gateway
+    app.kubernetes.io/part-of: mk-labs
+  annotations:
+    # TLS certificate managed by cert-manager
+    cert-manager.io/cluster-issuer: letsencrypt-prod
+spec:
+  ingressClassName: nginx
+  tls:
+    - hosts:
+        - connections.local.mk-labs.cloud
+      secretName: connections-tls
+  rules:
+    - host: connections.local.mk-labs.cloud
+      http:
+        paths:
+          - path: /
+            pathType: Prefix
+            backend:
+              service:
+                name: connections
+                port:
+                  number: 8080