feat: unified food calendar — extend home screen to future dates + planned meals

Phase 1: date strip now covers today + 7 future days; right chevron enabled;
future pills rendered in lighter style.

Phase 2: home screen shows DateContext (past/today/future):
- future dates: hide calorie ring + macros, show PlanningBanner
- plannedMealsProvider derives from cached menuProvider (no extra API call)
- _MealCard shows ghost PlannedSlotTile for unconfirmed menu slots
- "Mark as eaten" creates a diary entry (source: menu_plan) via existing API

New l10n keys (12 locales): planningForDate, markAsEaten, plannedMealLabel

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

client/lib/l10n/app_localizations.dart

@@ -789,6 +789,24 @@ abstract class AppLocalizations {
   /// In en, this message translates to:
   /// **'Scan photo'**
   String get scanDishPhoto;
+
+  /// No description provided for @planningForDate.
+  ///
+  /// In en, this message translates to:
+  /// **'Planning for {date}'**
+  String planningForDate(String date);
+
+  /// No description provided for @markAsEaten.
+  ///
+  /// In en, this message translates to:
+  /// **'Mark as eaten'**
+  String get markAsEaten;
+
+  /// No description provided for @plannedMealLabel.
+  ///
+  /// In en, this message translates to:
+  /// **'Planned'**
+  String get plannedMealLabel;
 }
 
 class _AppLocalizationsDelegate