Replace AudioFile with AudioTrack, fix download+orphan+MD5 sync, always play original audio fallback

AudioTrack table replaces AudioFile (Filename, Name, AssignedFrequency,
MD5, Selected, Order) — fixes relative-path bug in scrollerPage.go that
caused "file not found" for single-track selection.

Download goroutine now:
  - Accepts *gorm.DB and updates AudioTrack.MD5 after each download.
  - Treats checksums.md5 as source of truth: removes local files and DB
    records not in the manifest (orphans).
  - Strips "./" prefix from manifest filenames (GNU md5sum format).

AudioOptions.go seeds 14 AudioTrack records matching server checksums.md5.
List background quad width matches the widest item (+ padding), centered.

scrollerPage.go switchAudioForFrequency falls back to original/selected
audio when a frequency has no matching track or file.  playOriginalAudio
is a no-op on repeat calls to avoid 5-second audio restart loop.

Fixes progress display: passes Max=0 during downloads so Home page shows
"x / X Files Downloaded" text instead of bogus "100.0%" percentage.

Downstream audio switching (DynamicAudio) verifies an AudioTrack exists
for the frequency before assigning it to a stream — frequencies without
a track (e.g. 528 Hz) gracefully use original audio instead.

internal/page/scrollerPage.go

@@ -38,6 +38,7 @@ type ScrollerPage struct {
 
 	audioRetryTimer float32
 	audioStarted    bool
+	originalAudioStarted bool
 	dynamicAudio    bool
 
 	lines         *LineDeque
@@ -284,34 +285,32 @@ func (p *ScrollerPage) Init(ctx *PageCtx) error {
 	logger.Info("DynamicAudio mode: %v", p.dynamicAudio)
 
 	// Start audio for the first proclamation in the stream.
-	started := false
-	if len(p.streams) > 0 {
-		if p.dynamicAudio {
-			started = p.switchAudioForFrequency(p.streams[0].frequencyValue)
-		}
+	if len(p.streams) > 0 && p.dynamicAudio {
+		p.switchAudioForFrequency(p.streams[0].frequencyValue)
+		p.audioStarted = true
 	}
 
-	if !started {
-		// Non-dynamic mode or frequency-specific file not yet available.
-		// Play whatever track is marked Selected in the audio_files table.
-		var selectedAudio db.AudioFile
-		if err := p.Context.DbPtr.Where("Selected = ?", true).First(&selectedAudio).Error; err != nil {
-			selectedAudio = db.AudioFile{
-				Name:     "OriginalAudio",
-				Path:     filepath.Join(audioDir(), "OriginalAudio.wav"),
-				Selected: true,
-				Order:    0,
+	if !p.audioStarted && !p.dynamicAudio {
+		// Static track selected in Audio Options.  Play whatever track is
+		// marked Selected in the audio_tracks table.
+		var selectedTrack db.AudioTrack
+		if err := p.Context.DbPtr.Where("selected = ?", true).First(&selectedTrack).Error; err != nil {
+			logger.Warning("No selected audio track found, audio will start when a track is chosen")
+		} else {
+			path := filepath.Join(audioDir(), selectedTrack.Filename)
+			if _, err := os.Stat(path); err == nil {
+				logger.Info("Playing %s", path)
+				if err := mixer.Play(path, true, config); err != nil {
+					logger.Error("Mixer returned an error: %v", err)
+				} else {
+					p.audioStarted = true
+				}
+			} else {
+				logger.Warning("Selected audio file %s not found yet (download may still be in progress)", path)
 			}
 		}
-
-		logger.Info("Playing %s", selectedAudio.Path)
-		if err := mixer.Play(selectedAudio.Path, true, config); err != nil {
-			logger.Error("Mixer returned an error: %v", err)
-		}
 	}
 
-	p.audioStarted = started
-
 	currentDevice := mixer.CurrentDevice()
 	if currentDevice == "" {
 		currentDevice = "default"
@@ -438,36 +437,55 @@ func audioDir() string {
 	return filepath.Join(home, ".radiantwave", "audio")
 }
 
-// audioPathForFrequency builds the on-disk path for a solfeggio frequency's
-// audio file, e.g. 396 -> "~/.radiantwave/audio/396Hz.wav".
-func (p *ScrollerPage) audioPathForFrequency(freq int) string {
-	return filepath.Join(audioDir(), fmt.Sprintf("%dHz.wav", freq))
-}
-
 // switchAudioForFrequency swaps the currently playing track to match freq.
+// If freq is 0 or no audio track exists for it, falls back to the original
+// / selected audio track (so audio never goes silent in Ready state).
 //
-//   - freq == 0 ("no specific frequency", i.e. the default proclamation) is
-//     always a no-op — whatever is playing keeps playing.
-//   - If freq already matches what's playing, nothing happens.
-//   - If the matching file doesn't exist on disk yet, the current track
-//     keeps playing untouched (so missing solfeggio audio never causes
-//     silence — and starts working automatically once the file is added).
-//   - Otherwise the current track is stopped immediately and freq's track
-//     starts right away (hard cut, no fade).
-//
-// Returns true if freq's track is now playing (either just switched, or
-// already was).
+// Returns true if audio is now playing (either frequency-specific or fallback).
 func (p *ScrollerPage) switchAudioForFrequency(freq int) bool {
-	if freq == 0 {
-		return false
-	}
-	if freq == p.currentAudioFreq {
+	if freq != 0 && freq == p.currentAudioFreq {
 		return true
 	}
 
-	path := p.audioPathForFrequency(freq)
+	if freq != 0 {
+		if track, err := p.audioTrackForFrequency(freq); err == nil {
+			path := filepath.Join(audioDir(), track.Filename)
+			if _, err := os.Stat(path); err == nil {
+				config, err := db.GetConfig(p.Context.DbPtr)
+				if err != nil {
+					panic(err)
+				}
+				mixer.Stop(3000, config)
+				if err := mixer.Play(path, true, config); err != nil {
+					logger.Error("Mixer returned an error: %v", err)
+					return false
+				}
+				p.currentAudioFreq = freq
+				return true
+			}
+		}
+	}
+
+	return p.playOriginalAudio()
+}
+
+// playOriginalAudio plays the selected AudioTrack, or the OriginalAudio track
+// if nothing is selected. Returns true if audio started successfully.
+func (p *ScrollerPage) playOriginalAudio() bool {
+	if p.originalAudioStarted {
+		return true
+	}
+
+	var track db.AudioTrack
+	if err := p.Context.DbPtr.Where("selected = ?", true).First(&track).Error; err != nil {
+		if err := p.Context.DbPtr.Where("assigned_frequency = ?", 0).First(&track).Error; err != nil {
+			logger.Warning("No audio tracks available")
+			return false
+		}
+	}
+	path := filepath.Join(audioDir(), track.Filename)
 	if _, err := os.Stat(path); err != nil {
-		logger.Warning("No audio file for %dHz (%s), keeping current track", freq, path)
+		logger.Warning("Original audio file not found: %s", path)
 		return false
 	}
 	config, err := db.GetConfig(p.Context.DbPtr)
@@ -479,10 +497,17 @@ func (p *ScrollerPage) switchAudioForFrequency(freq int) bool {
 		logger.Error("Mixer returned an error: %v", err)
 		return false
 	}
-	p.currentAudioFreq = freq
+	p.originalAudioStarted = true
+	p.currentAudioFreq = 0
 	return true
 }
 
+func (p *ScrollerPage) audioTrackForFrequency(freq int) (db.AudioTrack, error) {
+	var track db.AudioTrack
+	err := p.Context.DbPtr.Where("assigned_frequency = ?", freq).First(&track).Error
+	return track, err
+}
+
 // nextLineWords gets words for the current line and advances proclamation stream when needed.
 func (p *ScrollerPage) nextLineWords() []string {
 	if len(p.streams) == 0 {
@@ -645,20 +670,29 @@ func (p *ScrollerPage) HandleEvent(event *sdl.Event) error {
 func (p *ScrollerPage) Update(dt float32) error {
 	p.updateAutoVelocity(dt)
 
-	// In dynamic mode, retry audio switch every 5 seconds until the
-	// frequency-specific file is found. In non-dynamic mode the selected
-	// file plays continuously — nothing to retry.
-	if p.dynamicAudio && !p.audioStarted {
+	// Periodically try to switch to the frequency-specific file in case
+	// it was just downloaded (only when the stream's frequency differs from
+	// whatever is currently playing).
+	if p.dynamicAudio && len(p.streams) > 0 {
 		p.audioRetryTimer += dt
 		if p.audioRetryTimer >= 5.0 {
 			p.audioRetryTimer = 0
-			if len(p.streams) > 0 {
-				freq := p.streams[p.streamIndex].frequencyValue
-				p.audioStarted = p.switchAudioForFrequency(freq) || freq == 0
+			freq := p.streams[p.streamIndex].frequencyValue
+			if freq != 0 && freq != p.currentAudioFreq {
+				p.switchAudioForFrequency(freq)
 			}
 		}
 	}
 
+	// Non-dynamic mode: retry selected track in case download just finished.
+	if !p.dynamicAudio && !p.audioStarted {
+		p.audioRetryTimer += dt
+		if p.audioRetryTimer >= 5.0 {
+			p.audioRetryTimer = 0
+			p.audioStarted = p.playOriginalAudio()
+		}
+	}
+
 	p.scrollOffset += dt * p.velocity
 	move := int32(p.scrollOffset)
 	if move == 0 {