feat: add dnsmasq DNS record admin UI

- store records in SQLite via built-in node:sqlite, no native deps
- wrap DB reads in await io() so they stay out of the static shell
- add CRUD pages backed by Server Actions with per-request data
- generate managed config and restart container via Docker socket
- add /resolve page to query dnsmasq for A and CNAME records
- add Dockerfile and compose setup with shared config volume

lib/action-state.ts

@@ -0,0 +1,12 @@
+import type { FieldErrors } from "./validate"
+
+/**
+ * Shared shape returned by every Server Action that a form consumes via `useActionState`.
+ * Kept in its own module because a `'use server'` file may only export async functions.
+ */
+export interface ActionState {
+  ok: boolean
+  message?: string
+  detail?: string
+  fieldErrors?: FieldErrors
+}