Implement comprehensive experience and leveling system

**NEW FEATURES:**
- Complete EXP system with Pokemon-style stat calculation
- Level-based stat growth and automatic HP restoration on level up
- Experience gain from catches and battle victories
- Visual level up notifications with stat increases

**EXPERIENCE SOURCES:**
- Successful catches: 5 EXP × caught pet level
- Wild battle victories: 10 EXP × defeated pet level
- Gym battle victories: 20 EXP × defeated pet level (2x multiplier)

**LEVELING MECHANICS:**
- Cubic growth formula: level³ × 4 - 12 (smooth progression)
- Level cap at 100
- Stats recalculated on level up using Pokemon formulas
- Full HP restoration on level up
- Real-time stat increase display

**EXPERIENCE DISPLAY:**
- \!team command now shows "EXP: X to next" for active pets
- Level up messages show exact stat gains
- Experience awarded immediately after catch/victory

**STAT CALCULATION:**
- HP: (2 × base + 31) × level / 100 + level + 10
- Other stats: (2 × base + 31) × level / 100 + 5
- Progressive growth ensures meaningful advancement

**BATTLE INTEGRATION:**
- EXP awarded after wild battles, gym individual battles, and catches
- Different multipliers for different victory types
- First active pet receives all experience

This creates proper RPG progression where pets grow stronger through gameplay,
encouraging both exploration (catches) and combat (battles) for advancement.

🤖 Generated with [Claude Code](https://claude.ai/code)

Co-Authored-By: Claude <noreply@anthropic.com>

modules/pet_management.py

@@ -41,7 +41,19 @@ class PetManagement(BaseModule):
         # Active pets with star
         for pet in active_pets:
             name = pet["nickname"] or pet["species_name"]
-            team_info.append(f"⭐{name} (Lv.{pet['level']}) - {pet['hp']}/{pet['max_hp']} HP")
+            
+            # Calculate EXP progress
+            current_exp = pet.get("experience", 0)
+            next_level_exp = self.database.calculate_exp_for_level(pet["level"] + 1)
+            current_level_exp = self.database.calculate_exp_for_level(pet["level"])
+            exp_needed = next_level_exp - current_exp
+            
+            if pet["level"] >= 100:
+                exp_display = "MAX"
+            else:
+                exp_display = f"{exp_needed} to next"
+            
+            team_info.append(f"⭐{name} (Lv.{pet['level']}) - {pet['hp']}/{pet['max_hp']} HP | EXP: {exp_display}")
         
         # Inactive pets  
         for pet in inactive_pets[:5]:  # Show max 5 inactive