fix(monitoring): rename bare Grafana dashboard JSONs out of *.json extension

ArgoCD's directory-driven manifest parser scans *.yaml AND *.json by
default. Bare Grafana dashboard JSONs (no apiVersion/kind/metadata)
poisoned manifest generation for the entire infra-monitoring Application
("Object 'Kind' is missing in <dashboard JSON>"), leaving sync state
Unknown.

These files are SOURCE for the file-provisioning path on noc1
(/opt/monitoring/grafana/dashboards/) and also get inlined into ConfigMap
wrappers like grafana-dashboard-remotedesktop.yaml. They are NOT K8s
manifests and shouldn't be in ArgoCD's manifest tree.

.argocdignore is for repo-level GitOps source eligibility, not for
filtering manifests within a directory-mode Application — the cleanest
fix is the *.txt extension that ArgoCD's parser skips.

Reverts the .argocdignore from the previous commit (didn't take effect).

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

apps/monitoring/.argocdignore

@@ -1,15 +0,0 @@
-# Bare Grafana dashboard JSON files are kept here as a CONVENIENCE source
-# for the file-provisioning path on noc1 (per
-# feedback_grafana_dashboard_shape_depends_on_noc1_delivery_path and
-# feedback_monitoring_k8s_target_vs_live_podman). They are NOT K8s
-# manifests — they have no `apiVersion` / `kind` / `metadata`. ArgoCD's
-# kubernetesIngress provider tries to unmarshal every file in the
-# directory and chokes on raw dashboard JSON with "Object 'Kind' is
-# missing", which then poisons manifest generation for the whole
-# infra-monitoring Application.
-#
-# When a dashboard needs to be K8s-deployed (i.e. file-provisioned via
-# Grafana sidecar in noc-monitoring.yaml), wrap the JSON in a ConfigMap
-# YAML next to it (see grafana-dashboard-remotedesktop.yaml as the
-# canonical pattern).
-*.json