feat: goal categories UI - complete rebuild
Completed frontend for multi-dimensional goal priorities.
**UI Changes:**
- Category-grouped goal display with color-coded headers
- Each category shows: icon, name, description, goal count
- Priority stars (⭐⭐⭐/⭐⭐/⭐) replace "PRIMÄR" badge
- Goals have category-colored left border
- Form fields: Category dropdown + Priority selector
- Removed "Gewichtung gesamt" display (useless UX)
**Categories:**
- 📉 Körper (body): Gewicht, Körperfett, Muskelmasse
- 🏋️ Training: Kraft, Frequenz, Performance
- 🍎 Ernährung: Kalorien, Makros, Essgewohnheiten
- 😴 Erholung: Schlaf, Regeneration, Ruhetage
- ❤️ Gesundheit: Vitalwerte, Blutdruck, HRV
- 📌 Sonstiges: Weitere Ziele
**Priority Levels:**
- ⭐⭐⭐ Hoch (1)
- ⭐⭐ Mittel (2)
- ⭐ Niedrig (3)
**Implementation:**
- Load groupedGoals via api.listGoalsGrouped()
- GOAL_CATEGORIES + PRIORITY_LEVELS constants
- handleEditGoal/handleSaveGoal/handleCreateGoal extended
- Backward compatible (is_primary still exists)
Next: Test migration + UI, then update Dashboard to show top-1 per category
Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>