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/LibraryPage.tsx

@@ -0,0 +1,68 @@
+import { useEffect, useState } from 'react'
+import { useParams } from 'react-router-dom'
+import toast from 'react-hot-toast'
+
+import { libraryAPI } from '../api/library'
+import type { Media } from '../types'
+import { MediaCard } from '../components/MediaCard'
+import { useAuthStore } from '../stores/auth'
+
+// Browse a single library. Admins also get a "scan" button that triggers
+// a fresh scan run on the backend.
+export function LibraryPage() {
+  const { id = '' } = useParams()
+  const role = useAuthStore((s) => s.user?.role)
+  const [items, setItems] = useState<Media[]>([])
+  const [total, setTotal] = useState(0)
+  const [loading, setLoading] = useState(true)
+  const [scanning, setScanning] = useState(false)
+
+  useEffect(() => {
+    if (!id) return
+    setLoading(true)
+    libraryAPI
+      .listMedia(id)
+      .then((d) => {
+        setItems(d.items)
+        setTotal(d.total)
+      })
+      .finally(() => setLoading(false))
+  }, [id])
+
+  const handleScan = async () => {
+    setScanning(true)
+    try {
+      const r = await libraryAPI.scan(id)
+      toast.success(`扫描完成:新增 ${r.added} 个文件`)
+      const d = await libraryAPI.listMedia(id)
+      setItems(d.items)
+      setTotal(d.total)
+    } catch {
+      toast.error('扫描失败')
+    } finally {
+      setScanning(false)
+    }
+  }
+
+  return (
+    <div className="space-y-6">
+      <div className="flex items-center justify-between">
+        <h1 className="font-display text-3xl font-bold text-white">
+          媒体库 <span className="text-slate-500">({total})</span>
+        </h1>
+        {role === 'admin' && (
+          <button onClick={handleScan} disabled={scanning} className="neon-button">
+            {scanning ? '扫描中…' : '立即扫描'}
+          </button>
+        )}
+      </div>
+
+      {loading && <p className="text-slate-500">加载中…</p>}
+      <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>
+  )
+}