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.

lib/config/schema.ts

@@ -2,6 +2,10 @@ import { z } from "zod";
 
 const searchEngineSchema = z.enum(["duckduckgo", "google", "bing"]);
 
+const durationSchema = z
+  .string()
+  .regex(/^\d+(ms|s|m|h)$/, 'Expected a duration like "500ms", "5s", "1m", or "1h"');
+
 export const bookmarkWidgetSchema = z.object({
   type: z.literal("bookmark"),
   name: z.string(),
@@ -15,9 +19,28 @@ export const searchWidgetSchema = z.object({
   defaultEngine: searchEngineSchema.optional(),
 });
 
+export const dockerWidgetSchema = z.object({
+  type: z.literal("docker"),
+  name: z.string(),
+  containerName: z.string(),
+  href: z.string().url().optional(),
+  showStats: z.boolean().default(true),
+  interval: durationSchema.default("5s"),
+});
+
+export const databaseWidgetSchema = z.object({
+  type: z.literal("database"),
+  name: z.string(),
+  containerName: z.string(),
+  engine: z.enum(["postgres", "redis"]),
+  interval: durationSchema.default("10s"),
+});
+
 export const widgetSchema = z.discriminatedUnion("type", [
   bookmarkWidgetSchema,
   searchWidgetSchema,
+  dockerWidgetSchema,
+  databaseWidgetSchema,
 ]);
 
 export const groupSchema = z.object({