refactor(docs): replace deprecated strings.Title with cases.Title

strings.Title has been deprecated since Go 1.18 because it does not
handle Unicode properly. Replace it with cases.Title from
golang.org/x/text which correctly handles language-specific title
casing. Applied to breadcrumb generation and document title formatting.

internal/docs/navigation.go

@@ -5,6 +5,9 @@ import (
 	"strings"
 
 	"bookhoard/templates"
+
+	"golang.org/x/text/cases"
+	"golang.org/x/text/language"
 )
 
 // BuildNavigation creates the navigation structure from the docs filesystem
@@ -100,7 +103,7 @@ func (h *DocsHandler) getDocTitle(docPath string) string {
 	filename := parts[len(parts)-1]
 
 	// Convert to title case
-	title = strings.Title(strings.ReplaceAll(filename, "-", " "))
+	title = cases.Title(language.English).String(strings.ReplaceAll(filename, "-", " "))
 
 	// Handle special cases
 	switch filename {