feat(wails): add native file dialogs and video streaming

FileService exposes open/save dialogs for video, project JSON, and WAV
export. User-selected videos stream from disk at /localmedia/video with
range request support for seeking in the webview.

Co-authored-by: Cursor <cursoragent@cursor.com>

main.go

@@ -3,6 +3,7 @@ package main
 import (
 	"embed"
 	"log"
+	"net/http"
 
 	"github.com/wailsapp/wails/v3/pkg/application"
 )
@@ -11,21 +12,35 @@ import (
 var assets embed.FS
 
 func main() {
+	var fileService *FileService
+
 	app := application.New(application.Options{
 		Name:        "sfxkeeb",
 		Description: "Annotate keyboard key presses on a video timeline",
 		Assets: application.AssetOptions{
 			Handler: application.AssetFileServerFS(assets),
+			Middleware: func(next http.Handler) http.Handler {
+				return http.HandlerFunc(func(w http.ResponseWriter, r *http.Request) {
+					if r.URL.Path == localMediaVideoPath && fileService != nil {
+						fileService.serveVideo(w, r)
+						return
+					}
+					next.ServeHTTP(w, r)
+				})
+			},
 		},
 		Mac: application.MacOptions{
 			ApplicationShouldTerminateAfterLastWindowClosed: true,
 		},
 	})
 
+	fileService = NewFileService(app)
+	app.RegisterService(application.NewService(fileService))
+
 	app.Window.NewWithOptions(application.WebviewWindowOptions{
-		Title:  "sfxkeeb",
-		Width:  1280,
-		Height: 900,
+		Title:     "sfxkeeb",
+		Width:     1280,
+		Height:    900,
 		MinWidth:  960,
 		MinHeight: 600,
 		Mac: application.MacWindow{