feat(handlers): Add helper methods for hybrid SSR

- Add GetPendingRegistrationsData() to DeviceHandler
- Add GetQueueData() to QueueHandler
- Add template types: DeviceData, PendingRegistrationData, ConflictData, QueueItemData
- Add collection types: CollectionData, CollectionDetailData, BookData

All changes are non-breaking and preserve API compatibility

templates/types.go

@@ -11,3 +11,65 @@ type PageData struct {
 	User        User
 	CurrentPage string
 }
+
+type CollectionData struct {
+	ID          string
+	Name        string
+	Description string
+	Color       string
+	Icon        string
+}
+
+type CollectionDetailData struct {
+	ID          string
+	Name        string
+	Description string
+	Color       string
+	Icon        string
+}
+
+type BookData struct {
+	MediaItemID    string
+	Title          string
+	Author         string
+	CoverImagePath string
+}
+
+type DeviceData struct {
+	ID            string
+	DeviceName    string
+	DeviceType    string
+	SyncEnabled   bool
+	AutoSync      bool
+	SyncFrequency int32
+	LastSync      string
+	LastSeen      string
+}
+
+type PendingRegistrationData struct {
+	RegistrationID string
+	DeviceName     string
+	DeviceType     string
+	ExpiresAt      string
+}
+
+type ConflictData struct {
+	ID               string
+	MediaItemID      string
+	MediaItemTitle   string
+	ConflictType     string
+	ResolutionStatus string
+	CreatedAt        string
+}
+
+type QueueItemData struct {
+	ID         string
+	DeviceID   string
+	DeviceName string
+	DeviceType string
+	SyncType   string
+	Status     string
+	Priority   int32
+	Attempts   int32
+	CreatedAt  string
+}