Moves the `heal` skill trigger from `on_attack` to `preBattle`, allowing cards to restore HP before combat begins. Updates `data/cards.json` to reflect new skill configurations (changing `strike`/`armored` to `swipe`/`heal` for specific cards).
Changes include:
- **Data**: Updated `skills.json` descriptions and triggers. Modified `cards.json` to use the new `heal` skill with `preBattle` trigger.
- **Engine**: Refactored `CombatEngine` to collect `healFires` during pre-battle processing and removed legacy `healAll` event logic from the attack phase.
- **Logic**: Updated `SkillProcessor` to track heal targets and amounts in the context for animation purposes.
- **Visuals**: Added `sfx_heal` audio asset and implemented new animation sequences in `BattleScene` (`_processHealFires`, `_animateHealFire`, `_doHealSpriteAndHP`) featuring flying sprites, HP text pulses, and floating damage numbers.
- **State Management**: Added `_restoreHealForDisplay` and `_reapplyHeal` to handle state snapshots correctly during the pre-battle render phase.
