feat: allow dots in resource/folder names

internal/web/resources.go

@@ -12,7 +12,8 @@ import (
 
 // resourceNameRe restricts calendar/address book names to characters that
 // are safe as both a URL path segment and a filesystem directory name.
-var resourceNameRe = regexp.MustCompile(`^[a-zA-Z0-9_-]{1,64}$`)
+// Includes dots for hidden files/folders (Unix convention).
+var resourceNameRe = regexp.MustCompile(`^[a-zA-Z0-9._-]{1,64}$`)
 
 // hexColorRe validates the 6-digit hex color format produced by an HTML
 // <input type="color">, e.g. "#3b82f6".