feat(i18n): add locale dictionaries and pilot surfaces

src/i18n/locales.ts

@@ -0,0 +1,21 @@
+export const SUPPORTED_LOCALES = ["en", "es"] as const
+
+export type Locale = (typeof SUPPORTED_LOCALES)[number]
+
+export const FALLBACK_LOCALE: Locale = "en"
+export const DEFAULT_LOCALE_ENV_VAR = "STOCK_MANAGER_DEFAULT_LOCALE"
+export const LOCALE_COOKIE_NAME = "stock-manager-locale"
+
+export function isLocale(value: unknown): value is Locale {
+  return (
+    typeof value === "string" && SUPPORTED_LOCALES.includes(value as Locale)
+  )
+}
+
+export function resolveDefaultLocale(value: unknown): Locale {
+  return isLocale(value) ? value : FALLBACK_LOCALE
+}
+
+export function resolveLocale(value: unknown, fallback: Locale): Locale {
+  return isLocale(value) ? value : fallback
+}