feat: bootstrap MediaStationGo (Go + React rewrite of MediaStation)

Adopt the cropflre/nowen-video tech stack and rebuild the project from
scratch:

  - Backend: Go 1.25 + Gin + GORM + SQLite (WAL) + JWT + WebSocket hub.
    Layered packages config / database / model / repository / service /
    middleware / handler. Default admin (admin/admin123) seeded on first
    run; /api routes for auth, libraries, media, stream and admin
    panels. WebSocket scan-progress events at /api/ws.
  - Frontend: React 18 + Vite 5 + Tailwind 3.4 + Zustand + axios +
    react-router 6 + lucide-react + framer-motion + hls.js. Pages for
    Login / Home / Library / Search / MediaDetail / Player / Admin
    (Library, Users, Settings tabs).
  - Distribution: multi-arch Dockerfile (frontend -> backend -> Alpine
    runtime), docker-compose.yml, GitHub Actions for CI and GHCR
    publish, Makefile, env-prefixed config (MEDIASTATION_*).
  - Docs: README, CONTRIBUTING, .env.example, config.example.yaml.

Backend builds, vets and tests pass. Frontend builds via tsc -b && vite
build (250 kB JS / 16 kB CSS, gzipped 84 / 4 kB).

web/src/pages/HomePage.tsx

@@ -0,0 +1,44 @@
+import { useEffect, useState } from 'react'
+
+import { mediaAPI } from '../api/library'
+import { MediaCard } from '../components/MediaCard'
+import type { Media } from '../types'
+
+// Landing page: shows the most recently added media items across every
+// library. Once the scraper / continue-watching subsystems land we will
+// fold in additional rows here.
+export function HomePage() {
+  const [items, setItems] = useState<Media[]>([])
+  const [loading, setLoading] = useState(true)
+
+  useEffect(() => {
+    mediaAPI
+      .search('', 24)
+      .then((d) => setItems(d.items))
+      .finally(() => setLoading(false))
+  }, [])
+
+  return (
+    <div className="space-y-8">
+      <header>
+        <h1 className="font-display text-3xl font-bold text-white">最近添加</h1>
+        <p className="text-sm text-slate-400">最新被扫描入库的媒体内容</p>
+      </header>
+
+      {loading && <p className="text-slate-500">加载中…</p>}
+      {!loading && items.length === 0 && (
+        <div className="glass-panel">
+          <p className="text-slate-300">
+            还没有任何媒体。前往 <span className="text-primary-400">管理后台</span>{' '}
+            创建媒体库,然后触发一次扫描。
+          </p>
+        </div>
+      )}
+      <div className="grid grid-cols-2 gap-4 sm:grid-cols-3 md:grid-cols-4 lg:grid-cols-5 xl:grid-cols-6">
+        {items.map((m) => (
+          <MediaCard key={m.id} media={m} />
+        ))}
+      </div>
+    </div>
+  )
+}