Chemical - Add radiation system

[AtrixZockt]

When merged this pull request will:

• Add a full radiation layer to the Chemical addon with four radiation types (alpha, beta, gamma, neutron), each with its own shielding and route of harm
• Add radiation sources (Eden + Zeus modules with presets, plus a carryable source object) and a wearable dosimeter with a geiger HUD and clicks
• Track dose properly: whole-body dose, localized skin burns (new KAT_RadiationBurn wound), inhaled internal contamination, and surface contamination that spreads to nearby units
• Hook radiation sickness into the existing KAT medical sims (anemia, failed clotting, GI/acidosis, hypotension, fever), plus a wound-infection to sepsis model and a screen effect
• Add the treatment chain: decontamination, KI, Prussian blue, antibiotics, filgrastim, antiemetic, and dose-estimation/survey diagnostics
• Make lethal doses survivable through a hard, sustained intensive-care protocol (stem-cell rescue) that works alongside the cardiac-arrest and advanced-rhythm systems
• Add CBA settings for the whole system, English and German strings, and a player/mission-maker documentation set

Still to do

• Real geiger click sounds (the dosimeter currently reuses placeholder chime samples)
• Dedicated dosimeter model, inventory icon, and HUD graphic
• Proper icons and models for the medication items (KI, Prussian blue, antibiotics, filgrastim, antiemetic, stem-cell rescue)
• A proper model and editor icon for the radioactive source object
• Further gameplay polish and balance tuning

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