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/stores/auth.ts

@@ -0,0 +1,27 @@
+import { create } from 'zustand'
+import { persist } from 'zustand/middleware'
+
+import type { User } from '../types'
+
+// Single source of truth for the authenticated user + JWT.
+// Persisted to localStorage so a page reload does not drop the session.
+interface AuthState {
+  token: string | null
+  user: User | null
+  setSession: (token: string, user: User) => void
+  setUser: (user: User) => void
+  logout: () => void
+}
+
+export const useAuthStore = create<AuthState>()(
+  persist(
+    (set) => ({
+      token: null,
+      user: null,
+      setSession: (token, user) => set({ token, user }),
+      setUser: (user) => set({ user }),
+      logout: () => set({ token: null, user: null }),
+    }),
+    { name: 'mediastationgo-auth' },
+  ),
+)