Updated PLANS.md, AGENTS.md, and arabic-localization.md to reflect the “foundations now, full translations later” approach and marked progress accordingly.

Implemented localization foundations across backend and frontend (locale settings/middleware, preferred language, i18n wiring, RTL support, minimal Arabic UI strings, Accept-Language).
Added targeted backend and frontend tests plus a risks note for pending full translation coverage.

backend/apps/accounts/middleware.py

@@ -0,0 +1,28 @@
+from django.utils import translation
+
+
+class UserLocaleMiddleware:
+    def __init__(self, get_response):
+        self.get_response = get_response
+
+    def __call__(self, request):
+        language = None
+        activated = False
+        user = getattr(request, "user", None)
+        if user and getattr(user, "is_authenticated", False):
+            language = getattr(user, "preferred_language", None)
+            if language:
+                translation.activate(language)
+                request.LANGUAGE_CODE = language
+                activated = True
+
+        response = self.get_response(request)
+
+        active_language = translation.get_language()
+        if active_language:
+            response["Content-Language"] = active_language
+
+        if activated:
+            translation.deactivate()
+
+        return response