Final cleanup: Update remaining comments and variable names

Changes:
- Update comments: "Bookmann UUID" → "Bookhoard UUID"
- Rename sidecar struct field: Bookmann → Bookhoard
- Update type names: SidecarBookmannConfig → SidecarBookhoardConfig
- Fix test database name in queue_test.go
- Fix uppercase env var examples in KOBO_SETUP.md

Internal Go variable names (BookmannUuid, bookmannUUID) left unchanged
as they're implementation details that don't affect functionality.

Part of project rename to Bookhoard.

internal/services/book_matching_test.go

@@ -11,7 +11,7 @@ func TestBookMatchingService_QueryBooks(t *testing.T) {
 	// This is a placeholder test that would need a mock database
 	// For now, we'll test the matching priority logic structure
 
-	t.Run("Priority 1: Bookmann UUID match", func(t *testing.T) {
+	t.Run("Priority 1: Bookhoard UUID match", func(t *testing.T) {
 		// Test that UUID matching returns highest confidence
 		req := &BookQueryRequest{
 			Identifiers: []string{"uuid:550e8400-e29b-41d4-a716-446655440000"},