Complete preset management implementation

- Add comprehensive preset reading functionality with helper methods
- Implement GetNextAvailablePresetSlot() and IsCurrentContentPresetable()
- Add CLI support for viewing presets with -presets flag
- Fix Preset XML tag to use lowercase 'preset' for API compliance
- Update documentation to reflect official API design:
  * GET /presets: fully implemented with rich analysis
  * POST /presets: officially 'N/A' per Bose documentation (not supported by design)
- Add detailed PRESET-MANAGEMENT.md documentation
- Update API endpoints overview and project status
- All tests passing with real device validation

Preset management is now 100% complete according to official API specification.
Read operations provide comprehensive preset analysis, while creation
is intentionally handled by official app/hardware controls per API design.

pkg/client/client.go

@@ -126,6 +126,36 @@ func (c *Client) GetPresets() (*models.Presets, error) {
 	return &presets, nil
 }
 
+// GetNextAvailablePresetSlot returns the next available preset slot (1-6), or error if all are used
+func (c *Client) GetNextAvailablePresetSlot() (int, error) {
+	presets, err := c.GetPresets()
+	if err != nil {
+		return 0, fmt.Errorf("failed to get presets: %w", err)
+	}
+
+	emptySlots := presets.GetEmptyPresetSlots()
+	if len(emptySlots) == 0 {
+		return 0, fmt.Errorf("all preset slots are occupied")
+	}
+
+	// Return the first available slot
+	return emptySlots[0], nil
+}
+
+// IsCurrentContentPresetable checks if the currently playing content can be saved as a preset
+func (c *Client) IsCurrentContentPresetable() (bool, error) {
+	nowPlaying, err := c.GetNowPlaying()
+	if err != nil {
+		return false, fmt.Errorf("failed to get now playing: %w", err)
+	}
+
+	if nowPlaying.IsEmpty() || nowPlaying.ContentItem == nil {
+		return false, nil
+	}
+
+	return nowPlaying.ContentItem.IsPresetable, nil
+}
+
 // SendKey sends a key press command to the device (press followed by release)
 func (c *Client) SendKey(keyValue string) error {
 	if !models.IsValidKey(keyValue) {

pkg/models/presets.go

@@ -14,6 +14,7 @@ type Presets struct {
 
 // Preset represents an individual preset
 type Preset struct {
+	XMLName     xml.Name     `xml:"preset"`
 	ID          int          `xml:"id,attr"`
 	CreatedOn   *int64       `xml:"createdOn,attr,omitempty"`
 	UpdatedOn   *int64       `xml:"updatedOn,attr,omitempty"`