refactor(utils): one PgTextString for the four pgtype.Text unwrappers

handlers textToString, router textToString, router getText, and utils
normText were four copies of the same NULL-to-empty unwrap (99 call
sites). One exported utils.PgTextString replaces them all; the private
normText (comparison normalizer) stays but is now the odd one out.

Harness fix found on the way: setupTestServer built a full wiring
literal for route registration and then RETURNED a second, sparser
literal that never copied AnnotationService — setup.AnnotationService
was always nil on the struct every test receives. Nobody noticed until
cross_library_move_test became the first caller (it previously used
the now-retired plain CreateMediaHighlight query); it now exercises
the real SaveHighlight path through the wired service.

internal/handlers/collections_test.go

@@ -4,6 +4,7 @@ import (
 	"testing"
 
 	"bookhoard/internal/database"
+	"bookhoard/internal/utils"
 
 	"github.com/jackc/pgx/v5/pgtype"
 	"github.com/stretchr/testify/assert"
@@ -103,7 +104,7 @@ func TestTextToString(t *testing.T) {
 
 	for _, tt := range tests {
 		t.Run(tt.name, func(t *testing.T) {
-			result := textToString(tt.input)
+			result := utils.PgTextString(tt.input)
 			assert.Equal(t, tt.expected, result)
 		})
 	}