adding abilities, created skill tree template and unlock mechanics

api/app/data/abilities/curse_of_agony.yaml

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+# Curse of Agony - Necromancer Dark Affliction ability
+# Heavy shadow DoT
+
+ability_id: "curse_of_agony"
+name: "Curse of Agony"
+description: "Curse your target with unbearable agony, dealing increasing shadow damage over 5 turns"
+ability_type: "spell"
+base_power: 10
+damage_type: "shadow"
+scaling_stat: "intelligence"
+scaling_factor: 0.55
+mana_cost: 28
+cooldown: 4
+is_aoe: false
+target_count: 1
+effects_applied:
+  - effect_id: "agony"
+    name: "Curse of Agony"
+    effect_type: "dot"
+    duration: 5
+    power: 12
+    stat_affected: null
+    stacks: 1
+    max_stacks: 1
+    source: "curse_of_agony"