fix(scanner): replace golang.org/x/text/cases.Title with manual titlecase to prevent panic on Unicode expansion

The cases.Title caser panicked with 'slice bounds out of range' when
processing certain Unicode characters that expand during case transformation
(e.g. ß → SS). This panic crashed the entire server during scanning, causing
WebSocket disconnections and failed scan requests.

internal/utils/tags.go

@@ -4,14 +4,8 @@ import (
 	"sort"
 	"strings"
 	"unicode"
-
-	"golang.org/x/text/cases"
-	"golang.org/x/text/language"
 )
 
-// titleCaser is a global caser for titlecase conversion
-var titleCaser = cases.Title(language.Und)
-
 // titlecase converts a string to title case while preserving hyphenation and apostrophes
 // Example: "science fiction" → "Science Fiction", "non-fiction" → "Non-Fiction", "o'reilly" → "O'Reilly"
 func titlecase(s string) string {
@@ -34,7 +28,12 @@ func titlecase(s string) string {
 			}
 			words[i] = result.String()
 		} else {
-			words[i] = titleCaser.String(word)
+			runes := []rune(word)
+			runes[0] = unicode.ToUpper(runes[0])
+			for j := 1; j < len(runes); j++ {
+				runes[j] = unicode.ToLower(runes[j])
+			}
+			words[i] = string(runes)
 		}
 	}
 	return strings.Join(words, " ")