fix: fix menu generation errors and show planned meals on home screen

Backend fixes:
- migration 003: add 'menu' value to recipe_source enum (was causing SQLSTATE 22P02)
- migration 004: rename recipe_products→recipe_ingredients, product_id→ingredient_id (was causing SQLSTATE 42P01)
- dish/repository.go: fix INSERT INTO tags using $1/$1 for two columns → $1/$2 (was causing SQLSTATE 42P08)
- home/handler.go: replace non-existent saved_recipes table with correct joins (recipes→dishes→dish_translations, user_saved_recipes) so today's plan and recommendations load correctly
- reqlog: new slog.Handler wrapper that adds request_id and stack trace to ERROR-level logs
- all handlers: slog.Error→slog.ErrorContext so error logs include request context; writeError includes request_id in response body

Client:
- home_screen.dart: extend home screen to future dates, show planned meals as ghost entries
- l10n: add new localisation keys for home screen date navigation and planned meal UI

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

client/lib/l10n/app_ar.arb

@@ -130,6 +130,10 @@
       "date": { "type": "String" }
     }
   },
-  "markAsEaten": "",
-  "plannedMealLabel": ""
+  "markAsEaten": "وضع علامة كمأكول",
+  "plannedMealLabel": "مخطط",
+  "generateWeekLabel": "تخطيط الأسبوع",
+  "generateWeekSubtitle": "سيقوم الذكاء الاصطناعي بإنشاء قائمة طعام تشمل الإفطار والغداء والعشاء لكامل الأسبوع",
+  "generatingMenu": "جارٍ إنشاء القائمة...",
+  "weekPlannedLabel": "تم تخطيط الأسبوع"
 }