feat: live docker/database widgets over WebSocket (M2)

Adds a custom server.ts (http server + Next request handler + a
noServer:true WebSocket server on /ws) so the app can push live data
without polling. A CollectorScheduler runs one interval-based job per
docker/database widget instance, backed by dockerode against
/var/run/docker.sock, and reconciles jobs when config.yml changes.

Config hot-reload is now fully wired: chokidar watches config.yml/.env,
re-validates on change, and broadcasts config:update (or a
non-destructive config:error, keeping the last-good config) to every
connected browser. The client subscribes to per-widget topics over a
single shared WebSocket with exponential-backoff reconnect and
last-result caching for instant resubscribe.

Verified end-to-end against real throwaway containers (nginx, redis):
live CPU/mem/uptime/health streamed over the socket, interval changes
picked up without a server restart, and a broken config.yml correctly
falls back to the last-valid config instead of crashing the app.

components/widgets/registry.ts

@@ -2,12 +2,17 @@ import type { ComponentType } from "react";
 import type { Widget } from "@/lib/config/schema";
 import { BookmarkWidget } from "./bookmark/Widget";
 import { SearchWidget } from "./search/Widget";
+import { DockerWidget } from "./docker/Widget";
+import { DatabaseWidget } from "./database/Widget";
 
 type WidgetComponent<T extends Widget["type"]> = ComponentType<{
   widget: Extract<Widget, { type: T }>;
+  widgetId: string;
 }>;
 
 export const widgetRegistry: { [K in Widget["type"]]: WidgetComponent<K> } = {
   bookmark: BookmarkWidget,
   search: SearchWidget,
+  docker: DockerWidget,
+  database: DatabaseWidget,
 };