refactor(media): replace hand-rolled SigV4 with maintained minio-go SDK; add /admin/media/upload endpoint

app/src/main.go

@@ -37,25 +37,16 @@ func main() {
 	log.Printf("loaded %d articles across %d subjects", len(c.Articles), len(c.Subjects))
 
 	s := NewSite(c)
-	// media proxy config (Garage S3)
-	s.Media = &S3MediaClient{
-		Endpoint: os.Getenv("KONTRA_S3_ENDPOINT"),
-		Bucket:   os.Getenv("KONTRA_S3_BUCKET"),
-		Key:      os.Getenv("KONTRA_S3_KEY"),
-		Secret:   os.Getenv("KONTRA_S3_SECRET"),
-		Client:   http.Client{},
-	}
-	if s.Media.Endpoint == "" {
-		s.Media.Endpoint = "http://127.0.0.1:3900"
-	}
-	if s.Media.Bucket == "" {
-		s.Media.Bucket = "kontra-day"
-	}
+	// media (Garage S3 via minio-go SDK)
+	s.Media = NewMediaClient()
 
 	// Routes — register specific paths BEFORE the catch-all.
 	http.HandleFunc("/media/{path...}", func(w http.ResponseWriter, r *http.Request) {
 		s.media(w, r, r.PathValue("path"))
 	})
+	http.HandleFunc("/admin/media/upload", func(w http.ResponseWriter, r *http.Request) {
+		s.mediaUpload(w, r)
+	})
 	http.HandleFunc("/subjects/{slug}", func(w http.ResponseWriter, r *http.Request) {
 		s.subject(w, r, r.PathValue("slug"))
 	})