Phase 06 Tier 1: Complete Backend Implementation - Recovery Tracking & Swap System

COMPLETED TASKS:
✅ 06-01: Workout Swap System
   - Added swapped_from_id to workout_logs
   - Created workout_swaps table for history
   - POST /api/workouts/:id/swap endpoint
   - GET /api/workouts/available endpoint
   - Reversible swaps with audit trail

✅ 06-02: Muscle Group Recovery Tracking
   - Created muscle_group_recovery table
   - Implemented calculateRecoveryScore() function
   - GET /api/recovery/muscle-groups endpoint
   - GET /api/recovery/most-recovered endpoint
   - Auto-tracking on workout log completion

✅ 06-03: Smart Workout Recommendations
   - GET /api/recommendations/smart-workout endpoint
   - 7-day workout analysis algorithm
   - Recovery-based filtering (>30% threshold)
   - Top 3 recommendations with context
   - Context-aware reasoning messages

DATABASE CHANGES:
- Added 4 new tables: muscle_group_recovery, workout_swaps, custom_workouts, custom_workout_exercises
- Extended workout_logs with: swapped_from_id, source_type, custom_workout_id, custom_workout_exercise_id
- Created 7 new indexes for performance

IMPLEMENTATION:
- Recovery service with 4 core functions
- 2 new route handlers (recovery, smartRecommendations)
- Updated workouts router with swap endpoints
- Integrated recovery tracking into POST /api/logs
- Full error handling and logging

TESTING:
- Test file created: /backend/test/phase-06-tests.js
- Ready for E2E and staging validation

STATUS: Ready for frontend integration and production review
Branch: feature/06-phase-06

frontend/src/components/MuscleGroupRecoveryList.css

@@ -0,0 +1,172 @@
+.muscle-recovery-list {
+  display: flex;
+  flex-direction: column;
+  gap: 20px;
+  padding: 16px;
+  background: #0a0a1f;
+  border-radius: 16px;
+}
+
+.muscle-recovery-header {
+  display: flex;
+  justify-content: space-between;
+  align-items: flex-start;
+  gap: 16px;
+}
+
+.muscle-recovery-header h2 {
+  margin: 0;
+  font-size: 20px;
+  font-weight: bold;
+  color: #fff;
+}
+
+.muscle-recovery-subtitle {
+  margin: 4px 0 0 0;
+  font-size: 13px;
+  color: #999;
+}
+
+.muscle-recovery-refresh {
+  background: none;
+  border: none;
+  color: #ccff00;
+  cursor: pointer;
+  padding: 8px;
+  border-radius: 8px;
+  transition: all 0.2s ease;
+  display: flex;
+  align-items: center;
+  justify-content: center;
+}
+
+.muscle-recovery-refresh:hover {
+  background: rgba(204, 255, 0, 0.1);
+  transform: rotate(180deg);
+}
+
+.muscle-recovery-loading {
+  display: flex;
+  flex-direction: column;
+  align-items: center;
+  justify-content: center;
+  gap: 16px;
+  padding: 40px 16px;
+  text-align: center;
+}
+
+.muscle-recovery-spinner {
+  width: 32px;
+  height: 32px;
+  border: 2px solid rgba(204, 255, 0, 0.2);
+  border-top: 2px solid #ccff00;
+  border-radius: 50%;
+  animation: spin 0.6s linear infinite;
+}
+
+@keyframes spin {
+  to {
+    transform: rotate(360deg);
+  }
+}
+
+.muscle-recovery-loading p {
+  color: #999;
+  font-size: 14px;
+  margin: 0;
+}
+
+.muscle-recovery-error {
+  display: flex;
+  align-items: center;
+  gap: 8px;
+  padding: 12px 16px;
+  background: rgba(255, 68, 68, 0.1);
+  border: 1px solid rgba(255, 68, 68, 0.3);
+  border-radius: 8px;
+  color: #ff8888;
+  font-size: 13px;
+}
+
+.muscle-recovery-empty {
+  padding: 40px 16px;
+  text-align: center;
+  color: #666;
+}
+
+.muscle-recovery-grid {
+  display: grid;
+  gap: 12px;
+}
+
+.muscle-recovery-grid--grid {
+  grid-template-columns: repeat(auto-fit, minmax(160px, 1fr));
+}
+
+.muscle-recovery-grid--list {
+  grid-template-columns: 1fr;
+}
+
+.muscle-recovery-item {
+  padding: 12px;
+  background: rgba(42, 42, 62, 0.6);
+  border: 1px solid rgba(204, 255, 0, 0.15);
+  border-radius: 10px;
+  cursor: pointer;
+  transition: all 0.2s ease;
+  display: flex;
+  flex-direction: column;
+  gap: 8px;
+}
+
+.muscle-recovery-item:hover {
+  background: rgba(42, 42, 62, 1);
+  border-color: rgba(204, 255, 0, 0.3);
+  transform: translateY(-2px);
+}
+
+.muscle-recovery-item-header {
+  display: flex;
+  justify-content: space-between;
+  align-items: baseline;
+  gap: 8px;
+}
+
+.muscle-recovery-name {
+  font-size: 14px;
+  font-weight: 600;
+  color: #fff;
+}
+
+.muscle-recovery-time {
+  font-size: 11px;
+  color: #888;
+  white-space: nowrap;
+}
+
+/* Responsive */
+@media (max-width: 768px) {
+  .muscle-recovery-grid--grid {
+    grid-template-columns: repeat(auto-fit, minmax(140px, 1fr));
+  }
+}
+
+@media (max-width: 480px) {
+  .muscle-recovery-list {
+    padding: 12px;
+    gap: 16px;
+  }
+
+  .muscle-recovery-header {
+    flex-direction: column;
+    align-items: flex-start;
+  }
+
+  .muscle-recovery-grid--grid {
+    grid-template-columns: repeat(2, 1fr);
+  }
+
+  .muscle-recovery-item {
+    padding: 10px;
+  }
+}