fitness: add kcal estimation based on Lytle et al. (2019) regression model

Estimate strength workout energy expenditure using the Lytle et al. multiple
linear regression model. Maps all 77 exercises to 7 studied categories with
confidence levels. Shows kcal on stats page (cumulative), session cards,
workout detail, and workout completion screen. Supports sex/height demographics
via profile section on measure page. Includes info tooltip with DOI reference.

src/models/FitnessGoal.ts

@@ -3,7 +3,9 @@ import mongoose from 'mongoose';
 const FitnessGoalSchema = new mongoose.Schema(
   {
     username: { type: String, required: true, unique: true },
-    weeklyWorkouts: { type: Number, required: true, default: 4, min: 1, max: 14 }
+    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 }
   },
   { timestamps: true }
 );
@@ -11,6 +13,8 @@ const FitnessGoalSchema = new mongoose.Schema(
 interface IFitnessGoal {
   username: string;
   weeklyWorkouts: number;
+  sex?: 'male' | 'female';
+  heightCm?: number;
 }
 
 let _model: mongoose.Model<IFitnessGoal>;