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_localizations.dart

@@ -807,6 +807,30 @@ abstract class AppLocalizations {
   /// In en, this message translates to:
   /// **'Planned'**
   String get plannedMealLabel;
+
+  /// No description provided for @generateWeekLabel.
+  ///
+  /// In en, this message translates to:
+  /// **'Plan the week'**
+  String get generateWeekLabel;
+
+  /// No description provided for @generateWeekSubtitle.
+  ///
+  /// In en, this message translates to:
+  /// **'AI will create a menu with breakfast, lunch and dinner for the whole week'**
+  String get generateWeekSubtitle;
+
+  /// No description provided for @generatingMenu.
+  ///
+  /// In en, this message translates to:
+  /// **'Generating menu...'**
+  String get generatingMenu;
+
+  /// No description provided for @weekPlannedLabel.
+  ///
+  /// In en, this message translates to:
+  /// **'Week planned'**
+  String get weekPlannedLabel;
 }
 
 class _AppLocalizationsDelegate