feat(rules): scale spell damage with caster level

DamageEffect gains optional scaling (1dX per N levels, capped) and scaling_flat (+X per N levels, capped) specs; effective_formula resolves them against the caster's level at cast time, so scaled dice flow through crits, energy resistance and metamagic like the base formula (CRB Magic - Caster Level). Loader rejects mismatched die types. Data: Fireball/Lightning Bolt 1d6/lvl max 10d6, Burning Hands 1d4/lvl max 5d4, Shocking Grasp 1d6/lvl max 5d6, Inflict Light Wounds +1/lvl max +5 (SRD-verified). Cure Light Wounds stays flat: its golden transcript pins 1d8+1 and HealEffect scaling is out of scope.

Ultraworked with [Sisyphus](https://github.com/code-yeongyu/oh-my-openagent)

Co-authored-by: Sisyphus <clio-agent@sisyphuslabs.ai>

data/spells/fireball.json

@@ -14,12 +14,13 @@
       "effects": [
         {
           "type": "damage",
-          "formula": "6d6",
+          "formula": "0",
           "types": ["fire"],
-          "half_on_save": true
+          "half_on_save": true,
+          "scaling": { "dice": "1d6", "per_levels": 1, "max_dice": 10 }
         }
       ]
     }
   ],
-  "description": "A glowing bead streaks from you and bursts into a 20-foot radius explosion of fire, dealing 6d6 points of fire damage. Reflex save for half."
+  "description": "A glowing bead streaks from you and bursts into a 20-foot radius explosion of fire, dealing 1d6 points of fire damage per caster level (maximum 10d6). Reflex save for half."
 }