feat(i18n): implement new locale resolution logic and service layer

lib/i18n/content.ts

@@ -33,8 +33,8 @@ export const contentTranslationRegistry = {
     { name: "description", label: "Açıklama", kind: "textarea", maxLength: 20_000, placeholder: "Kapsam, not veya teslim kriterleri..." },
   ],
   branding: [
-    { name: "portalWelcome", label: "Portal karşılama metni", kind: "textarea", maxLength: 10_000 },
-    { name: "portalFooter", label: "Portal footer metni", kind: "textarea", maxLength: 5_000 },
+    { name: "portalWelcome", label: "Portal karşılama metni", kind: "textarea", maxLength: 2_000 },
+    { name: "portalFooter", label: "Portal footer metni", kind: "textarea", maxLength: 1_000 },
   ],
   calendar_event: [
     { name: "title", label: "Başlık", required: true, maxLength: 300 },

lib/i18n/locale-resolution.ts

@@ -0,0 +1,78 @@
+export type LocaleCandidate = {
+  code: string;
+  status: "draft" | "active" | "archived" | "test";
+  textDirection: "ltr" | "rtl";
+};
+
+export type LocaleResolutionSource =
+  | "client"
+  | "fallback"
+  | "instance"
+  | "invitation"
+  | "user";
+
+export type LocaleResolution = {
+  locale: string;
+  requestedLocale: string | null;
+  defaultLocale: string;
+  direction: "ltr" | "rtl";
+  source: LocaleResolutionSource;
+};
+
+type ResolveLocalePolicyInput = {
+  activeLocales: readonly LocaleCandidate[];
+  defaultLocale: string | null | undefined;
+  candidates: ReadonlyArray<{
+    locale: string | null | undefined;
+    source: Exclude<LocaleResolutionSource, "fallback" | "instance">;
+  }>;
+  fallbackLocale?: string;
+};
+
+export function resolveLocalePolicy(input: ResolveLocalePolicyInput): LocaleResolution {
+  const fallbackLocale = input.fallbackLocale ?? "tr";
+  const activeLocales = new Map(
+    input.activeLocales
+      .filter((locale) => locale.status === "active")
+      .map((locale) => [locale.code, locale] as const),
+  );
+  const safeDefault = activeLocales.has(input.defaultLocale ?? "")
+    ? input.defaultLocale!
+    : activeLocales.has(fallbackLocale)
+      ? fallbackLocale
+      : activeLocales.keys().next().value ?? fallbackLocale;
+
+  for (const candidate of input.candidates) {
+    const requestedLocale = normalizeLocaleCode(candidate.locale);
+    if (!requestedLocale) continue;
+    const locale = activeLocales.get(requestedLocale);
+    if (!locale) continue;
+
+    return {
+      locale: locale.code,
+      requestedLocale,
+      defaultLocale: safeDefault,
+      direction: locale.textDirection,
+      source: candidate.source,
+    };
+  }
+
+  const defaultRecord = activeLocales.get(safeDefault);
+  return {
+    locale: safeDefault,
+    requestedLocale: normalizeLocaleCode(input.defaultLocale),
+    defaultLocale: safeDefault,
+    direction: defaultRecord?.textDirection ?? directionForLocale(safeDefault),
+    source: activeLocales.has(input.defaultLocale ?? "") ? "instance" : "fallback",
+  };
+}
+
+export function normalizeLocaleCode(value: string | null | undefined): string | null {
+  if (!value) return null;
+  const normalized = value.trim();
+  return /^[a-z]{2}(?:-[A-Z]{2}[0-9]?)?$/.test(normalized) ? normalized : null;
+}
+
+export function directionForLocale(locale: string): "ltr" | "rtl" {
+  return /^(ar|fa|he|ur)(-|$)/.test(locale) ? "rtl" : "ltr";
+}