fix: prevent form reset on error, add multi-select for goal/activity/injury

- Remove profileNextStep(1) from saveProfile catch block so users stay
  on current step when an error occurs instead of being sent back to step 1
- Convert Goal, Activity Level, and Injury Area fields from single-select
  (radio/dropdown) to multi-select checkboxes with comma-separated storage
- Add validateMultiEnum backend validation for comma-separated enum values
- Update trainer.js filterByInjury and goal checks for multi-value support
- Update dietitian.js TDEE, calorie, and water calculations for multi-values

Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>

src/services/trainer.js

@@ -406,9 +406,16 @@ function pickRandom(arr, count) {
   return shuffled.slice(0, Math.min(count, arr.length));
 }
 
+function hasGoal(profile, goalValue) {
+  const goal = profile.goal || "maintain";
+  return goal.split(",").map((s) => s.trim()).includes(goalValue);
+}
+
 function filterByInjury(exercises, injuryArea) {
   if (!injuryArea || injuryArea === "none") return exercises;
-  return exercises.filter((e) => !e.contraindicated_injuries.includes(injuryArea));
+  const areas = String(injuryArea).split(",").map((s) => s.trim()).filter((s) => s && s !== "none");
+  if (areas.length === 0) return exercises;
+  return exercises.filter((e) => !areas.some((area) => e.contraindicated_injuries.includes(area)));
 }
 
 function filterByConditions(exercises, profile) {
@@ -743,7 +750,8 @@ function buildInjuryNote(profile) {
     mild: "mild", moderate: "moderate", severe: "severe",
   };
 
-  const areaName = areaNames[profile.injury_area] || profile.injury_area;
+  const areas = String(profile.injury_area).split(",").map((s) => s.trim()).filter((s) => s && s !== "none");
+  const areaName = areas.map((a) => areaNames[a] || a).join(", ");
   const severityName = severityNames[profile.injury_severity] || "mild";
   let note = `Program adapted for ${severityName} ${areaName} injury.`;
 
@@ -872,7 +880,7 @@ function buildCardioDay(dayNumber, dayName, focus, profile, week) {
   const bodyType = profile.body_type || "mesomorph";
   let exercises = [];
 
-  if ((bodyType === "endomorph" || profile.goal === "lose_weight") && !profile.heart_condition) {
+  if ((bodyType === "endomorph" || hasGoal(profile, "lose_weight")) && !profile.heart_condition) {
     const safeHiit = filterByLocation(filterByEquipment(filterByConditions(filterByInjury(EXERCISES.hiit, injuryArea), profile), profile), location);
     const safeCardio = filterByLocation(filterByEquipment(filterByConditions(filterByInjury(EXERCISES.cardio, injuryArea), profile), profile), location);
     exercises = [...pickRandom(safeHiit, 4), ...pickRandom(safeCardio, 1)];
@@ -1120,7 +1128,6 @@ function generateWheelchairProgram(profile, week) {
 // ─────────────────────────────────────────────────────────────────────────────
 
 function applyGoalAdjustments(days, profile, week) {
-  const goal = profile.goal || "maintain";
   const bodyType = profile.body_type || "mesomorph";
   const location = profile.workout_location || "gym";
 
@@ -1130,7 +1137,7 @@ function applyGoalAdjustments(days, profile, week) {
     let modified = { ...day, exercises: [...day.exercises] };
 
     // For lose_weight: add cardio to strength days
-    if (goal === "lose_weight" && day.type === "strength" && !profile.heart_condition) {
+    if (hasGoal(profile, "lose_weight") && day.type === "strength" && !profile.heart_condition) {
       const injuryArea = profile.has_injury ? (profile.injury_area || "none") : "none";
       let safeCardio = filterByLocation(filterByEquipment(filterByConditions(filterByInjury(EXERCISES.cardio, injuryArea), profile), profile), location);
       if (safeCardio.length > 0) {
@@ -1154,7 +1161,7 @@ function applyGoalAdjustments(days, profile, week) {
     }
 
     // Gain weight: remove excess cardio from strength days
-    if (goal === "gain_weight") {
+    if (hasGoal(profile, "gain_weight")) {
       modified.exercises = modified.exercises.filter((e) => {
         return !EXERCISES.cardio.some((c) => c.name === e.name);
       });
@@ -1165,11 +1172,10 @@ function applyGoalAdjustments(days, profile, week) {
 }
 
 function adjustCardioRestDays(days, profile, week) {
-  const goal = profile.goal || "maintain";
   const bodyType = profile.body_type || "mesomorph";
   let cardioDaysNeeded = 0;
 
-  if (goal === "lose_weight" && !profile.heart_condition) cardioDaysNeeded = 2;
+  if (hasGoal(profile, "lose_weight") && !profile.heart_condition) cardioDaysNeeded = 2;
   else if (bodyType === "endomorph" && !profile.heart_condition) cardioDaysNeeded = 1;
 
   let converted = 0;