feat: add nutrition/food logging to fitness section

Daily food log with calorie and macro tracking against configurable diet
goals (presets: WHO balanced, cut, bulk, keto, etc.). Includes USDA/BLS
food search with portion-based units, favorite ingredients, custom
reusable meals, per-food micronutrient detail pages, and recipe-to-log
integration via AddToFoodLogButton. Extends FitnessGoal with nutrition
targets and adds birth year to user profile for BMR calculation.

src/models/FitnessGoal.ts

@@ -5,7 +5,14 @@ const FitnessGoalSchema = new mongoose.Schema(
     username: { type: String, required: true, unique: true },
     weeklyWorkouts: { type: Number, required: true, default: 4, min: 1, max: 14 },
     sex: { type: String, enum: ['male', 'female'], default: 'male' },
-    heightCm: { type: Number, min: 100, max: 250 }
+    heightCm: { type: Number, min: 100, max: 250 },
+    birthYear: { type: Number, min: 1900, max: 2020 },
+    activityLevel: { type: String, enum: ['sedentary', 'light', 'moderate', 'very_active'], default: 'light' },
+    dailyCalories: { type: Number, min: 500, max: 10000 },
+    proteinMode: { type: String, enum: ['fixed', 'per_kg'] },
+    proteinTarget: { type: Number, min: 0 },
+    fatPercent: { type: Number, min: 0, max: 100 },
+    carbPercent: { type: Number, min: 0, max: 100 },
   },
   { timestamps: true }
 );
@@ -15,6 +22,13 @@ interface IFitnessGoal {
   weeklyWorkouts: number;
   sex?: 'male' | 'female';
   heightCm?: number;
+  birthYear?: number;
+  activityLevel?: 'sedentary' | 'light' | 'moderate' | 'very_active';
+  dailyCalories?: number;
+  proteinMode?: 'fixed' | 'per_kg';
+  proteinTarget?: number;
+  fatPercent?: number;
+  carbPercent?: number;
 }
 
 let _model: mongoose.Model<IFitnessGoal>;