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).

internal/service/stream.go

@@ -0,0 +1,58 @@
+// Package service — direct-play / range request streaming.
+package service
+
+import (
+	"errors"
+	"net/http"
+	"os"
+
+	"go.uber.org/zap"
+
+	"github.com/ShukeBta/MediaStationGo/internal/config"
+	"github.com/ShukeBta/MediaStationGo/internal/repository"
+)
+
+// StreamService serves media files with proper Range support so browsers can
+// seek into the stream.
+//
+// HLS / on-demand transcoding is intentionally omitted from this initial
+// scaffold. The HTTP handler returns 501 (NotImplemented) for that path,
+// while direct-play already works for browser-friendly containers (mp4 /
+// webm / m4v).
+type StreamService struct {
+	cfg  *config.Config
+	log  *zap.Logger
+	repo *repository.Container
+}
+
+// NewStreamService is the constructor.
+func NewStreamService(cfg *config.Config, log *zap.Logger, repo *repository.Container) *StreamService {
+	return &StreamService{cfg: cfg, log: log, repo: repo}
+}
+
+// ErrMediaNotFound is returned when the media row or its file is missing.
+var ErrMediaNotFound = errors.New("media not found")
+
+// ServeFile streams the file backing the given media ID using
+// http.ServeContent so HEAD / Range / If-Modified-Since are handled for free.
+func (s *StreamService) ServeFile(w http.ResponseWriter, r *http.Request, mediaID string) error {
+	m, err := s.repo.Media.FindByID(r.Context(), mediaID)
+	if err != nil {
+		return err
+	}
+	if m == nil {
+		return ErrMediaNotFound
+	}
+	f, err := os.Open(m.Path)
+	if err != nil {
+		return ErrMediaNotFound
+	}
+	defer f.Close()
+	stat, err := f.Stat()
+	if err != nil {
+		return err
+	}
+	w.Header().Set("Accept-Ranges", "bytes")
+	http.ServeContent(w, r, stat.Name(), stat.ModTime(), f)
+	return nil
+}