Add menu bar and center playback controls

UI improvements:
- Add menu bar at top with File, View, and Tools menus
- Move File operations (Open, Add Folder, Clear) to File menu
- Add Frame-Accurate Mode toggle in Tools menu
- Center playback controls (Prev, Play, Next) at bottom
- Move volume controls to left, playlist toggle to right
- Remove redundant top control bar for cleaner interface
- Add keyframingMode state to appState for feature toggle

Layout changes:
- Menu bar provides access to advanced features
- Main player area takes full space below menu
- Controls centered bottom like modern video players (Haruna/VLC)
- Cleaner interface suitable for basic playback or advanced editing

Prepares for:
- Frame-accurate navigation features (when keyframing enabled)
- Timeline with keyframe markers
- In/out point cutting tools
- Integration with VideoTools chapter support

Co-Authored-By: Claude <noreply@anthropic.com>

main.go

@@ -197,6 +197,7 @@ type appState struct {
 	queueOffset      fyne.Position
 	compareFile1     *videoSource
 	compareFile2     *videoSource
+	keyframingMode   bool // Toggle for frame-accurate editing features
 }
 
 func (s *appState) stopPreview() {
@@ -558,14 +559,14 @@ func (s *appState) showPlayerView() {
 	s.stopCompareSessions()
 	s.active = "player"
 
-	header := widget.NewLabelWithStyle("VT Player", fyne.TextAlignLeading, fyne.TextStyle{Bold: true})
-
 	// Helper to refresh the view after selection/loads.
 	refresh := func() {
 		s.showPlayerView()
 	}
 
-	openFile := widget.NewButton("Open File…", func() {
+	// Create menu bar
+	fileMenu := fyne.NewMenu("File",
+		fyne.NewMenuItem("Open File…", func() {
 			dlg := dialog.NewFileOpen(func(r fyne.URIReadCloser, err error) {
 				if err != nil || r == nil {
 					return
@@ -576,9 +577,8 @@ func (s *appState) showPlayerView() {
 			}, s.window)
 			dlg.Resize(fyne.NewSize(700, 480))
 			dlg.Show()
-	})
-
-	addFolder := widget.NewButton("Add Folder…", func() {
+		}),
+		fyne.NewMenuItem("Open Folder…", func() {
 			dlg := dialog.NewFolderOpen(func(l fyne.ListableURI, err error) {
 				if err != nil || l == nil {
 					return
@@ -591,27 +591,38 @@ func (s *appState) showPlayerView() {
 			}, s.window)
 			dlg.Resize(fyne.NewSize(700, 480))
 			dlg.Show()
-	})
-
-	clearList := widget.NewButton("Clear Playlist", func() {
+		}),
+		fyne.NewMenuItemSeparator(),
+		fyne.NewMenuItem("Clear Playlist", func() {
 			s.clearVideo()
 			refresh()
-	})
-	clearList.Importance = widget.LowImportance
+		}),
+	)
+
+	viewMenu := fyne.NewMenu("View",
+		fyne.NewMenuItem("Playlist", func() {
+			// Will be implemented with playlist toggle
+		}),
+	)
 
-	var compareBtn *widget.Button
 	if len(s.loadedVideos) >= 2 {
-		compareBtn = widget.NewButton("Compare View", func() {
+		viewMenu.Items = append(viewMenu.Items, fyne.NewMenuItem("Compare Videos", func() {
 			s.showCompareView()
-		})
+		}))
 	}
 
-	barItems := []fyne.CanvasObject{openFile, addFolder, clearList}
-	if compareBtn != nil {
-		barItems = append(barItems, compareBtn)
-	}
-	barItems = append(barItems, layout.NewSpacer())
-	controlsBar := container.NewHBox(barItems...)
+	toolsMenu := fyne.NewMenu("Tools")
+
+	// Keyframing mode toggle
+	keyframeModeItem := fyne.NewMenuItem("Frame-Accurate Mode", func() {
+		s.keyframingMode = !s.keyframingMode
+		refresh()
+	})
+	keyframeModeItem.Checked = s.keyframingMode
+	toolsMenu.Items = append(toolsMenu.Items, keyframeModeItem)
+
+	mainMenu := fyne.NewMainMenu(fileMenu, viewMenu, toolsMenu)
+	s.window.SetMainMenu(mainMenu)
 
 	// Player area
 	var playerArea fyne.CanvasObject
@@ -836,7 +847,17 @@ func (s *appState) showPlayerView() {
 		progressBar := container.NewBorder(nil, nil, currentTime, totalTime, container.NewMax(slider))
 		volContainer := container.NewHBox(volIcon, container.NewMax(volSlider))
 		volContainer.Resize(fyne.NewSize(150, 32))
-		controlRow := container.NewHBox(prevBtn, playBtn, nextBtn, layout.NewSpacer(), playlistToggleBtn, volContainer)
+
+		// Center the playback controls
+		playbackControls := container.NewHBox(prevBtn, playBtn, nextBtn)
+
+		// Create control row with centered playback controls
+		controlRow := container.NewBorder(
+			nil, nil,
+			volContainer,  // Volume on left
+			container.NewHBox(playlistToggleBtn), // Playlist toggle on right
+			container.NewCenter(playbackControls), // Playback controls centered
+		)
 
 		playerArea = container.NewBorder(
 			nil,
@@ -847,13 +868,7 @@ func (s *appState) showPlayerView() {
 		)
 	}
 
-	mainPanel := container.NewBorder(
-		container.NewVBox(header, controlsBar, widget.NewSeparator()),
-		nil,
-		nil,
-		nil,
-		playerArea,
-	)
+	mainPanel := playerArea
 
 	s.setContent(mainPanel)
 }