Refactor Force and Monarch to Improve Encapsulation and Game Logic

[JaskRendix]

Changes:

• moved several calculations from Monarch into Force to improve encapsulation
• added isUnderprovisioned() to Force to determine whether naval capacity is sufficient for land units
• added downsizeToLimit(double) to handle strength‑based downsizing of forces
• added getCustomPrice(...) to compute mercenary pricing based on player‑specific purchase costs
• added downsizeToPrice(...) to reduce a force until it fits within a player’s available gold
• added scaleLandUnits(int) to support incremental growth of the Intervention Force
• added copy() to allow safe simulation of force adjustments without modifying the original
• simplified prepareToBoard(UnitType) to more cleanly ensure adequate naval transport capacity
• updated Monarch to use high‑level Force methods instead of manually iterating over unit lists
• simplified Intervention Force growth logic using new Force helpers
• improved war support logic by using downsizeToLimit to avoid overpowered assistance
• reduced duplication and clarified responsibilities: Monarch now decides when to act, while Force handles how to adjust units and capacity