feat(prometheus-direct-charting): slice 3 — remove grafana + config rewrite + changelog

Remove the entire Grafana surface: integrations/grafana.py, GrafanaWidgetSource
(+ _fetch_chart, now redundant since prometheus chart exists), GrafanaLinkWidget,
LinksTab, get_grafana_status endpoint, useGrafanaStatus hook, GrafanaStatus type,
fetchGrafanaStatus client fn, registry/nav/tab entries (FE+BE). Rewrite
config.yaml thin-dashboard rule to match reality (recharts is sanctioned for
Prometheus-backed series). CHANGELOG migration note added.

Backend: 293 pytest pass, ruff clean. Frontend: build+lint green (0 errors).
SC-115/116 grep-clean (only prometheus_range.py migration comments + Dashboard.test
shortcut fixture remain — both spec-allowed).

frontend/src/pages/service-tabs/index.ts

@@ -8,7 +8,6 @@ import type { ComponentType } from "react";
 import type { ServiceInstance } from "../../types";
 import { OverviewTab } from "./OverviewTab";
 import { AlertsTab } from "./AlertsTab";
-import { LinksTab } from "./LinksTab";
 import { MetricsTab } from "./MetricsTab";
 import { MediaTab } from "./MediaTab";
 import { RequestsTab } from "./RequestsTab";
@@ -56,8 +55,6 @@ export function serviceContentTabs(serviceType: string): ContentTab[] {
 			];
 		case "alertmanager":
 			return [{ label: "Alerts", Component: AlertsTab }];
-		case "grafana":
-			return [{ label: "Links", Component: LinksTab }];
 		case "prometheus":
 			return [{ label: "Metrics", Component: MetricsTab }];
 		default: