Add GraphQL API and service CRUD for cookie patterns

Add CookiePattern type, connection, and mutations to the GraphQL schema
with full resolver implementations. Add service methods for pattern
CRUD, category movement, listing, and counting. This enables the console
to manage cookie patterns instead of individual cookies.

Signed-off-by: Émile Ré <emile@getprobo.com>

pkg/cookiebanner/errors.go

@@ -34,4 +34,7 @@ var (
 	ErrCategoriesBannerMismatch   = errors.New("source and target categories belong to different banners")
 	ErrSameCategoryMove           = errors.New("source and target cookie categories must be different")
 	ErrPostHogConsentKindInvalid  = errors.New("PostHog consent can only be enabled on normal categories")
+	ErrCookiePatternNotFound      = errors.New("cookie pattern not found")
+	ErrPatternAlreadyExists       = errors.New("a pattern with this name already exists in this banner")
+	ErrSamePatternCategoryMove    = errors.New("source and target cookie categories must be different")
 )