Add a new `all` modifier to skills (`strike`, `pierce`, `mortar`, `rally`, `heal`, `enfeeble`, `weaken`, `rupture`) that targets all valid enemies or allies instead of a single target. This includes:
- **Data Layer**: Updated cards.json with expanded skill definitions and added new cards (Imperial Guardian, Pillager, Marauder). Added `allDescription` and `supportsAll` flags to skills.json.
- **Combat Logic**: Extended SkillProcessor and CombatEngine to handle "all" variants, managing parallel state updates for HP, armor, attack stats, and buffs/debuffs across multiple targets.
- **Visuals**: Implemented new animation sequences in BattleScene for area-of-effect skills (parallel projectiles, shared sound effects) and updated CardTooltip/CardObject to display the "all" modifier.
- **Audio**: Introduced a shuffled battle music playlist that cycles through multiple tracks during combat, resuming main menu music upon exit.
