feat(i18n): Hebrew locale + full RTL support

i18n/merge-messages.ts

@@ -0,0 +1,21 @@
+type Messages = Record<string, unknown>;
+
+/**
+ * Deep-merge `override` onto `base`, returning a new object. Keys present only
+ * in `base` survive — used to fall back to English for any string a locale has
+ * not translated yet, so the UI shows the English text rather than a raw
+ * message key (e.g. "settings.tabs.layout").
+ */
+export function mergeMessages(base: Messages, override: Messages): Messages {
+  const out: Messages = { ...base };
+  for (const key of Object.keys(override)) {
+    const b = out[key];
+    const o = override[key];
+    if (b && o && typeof b === 'object' && typeof o === 'object' && !Array.isArray(b) && !Array.isArray(o)) {
+      out[key] = mergeMessages(b as Messages, o as Messages);
+    } else {
+      out[key] = o;
+    }
+  }
+  return out;
+}