Add health/damage system for units

Objective

Create comprehensive health and damage system that tracks unit vitality and handles damage application for MVP combat.

Requirements

• Health Tracking: Each unit has health points and maximum health
• Damage Application: Units lose health when attacked
• Health Display: Health status visible to players
• Damage Types: Support for different damage types and resistances

Technical Details

• Implement unit health data structures and management
• Create damage calculation with armor/resistance systems
• Add health regeneration and healing mechanics
• Handle health state synchronization
• Implement health visualization systems
• Add damage number feedback and effects

Acceptance Criteria

• Units have health that decreases when taking damage
• Health is displayed visually for players to see
• Damage calculations account for unit stats and resistances
• Health state is synchronized across all clients
• Health system is performant for many units

Milestone Relation

Essential for MVP combat system. Required for meaningful combat outcomes and player feedback on battle progress.