feat: luck bonus, inventory slots bonus, multi-enhancements, magic skill modifier

- Add luck.bonus field to character DataModel; included in prepareDerivedData
   (luck.max = fate.rank + bonus); shown as editable +bonus field next to
   luck max in edit mode (same UX as grit bonus)

 - Add inventory.slotsBonus field to character DataModel; Equipment tab now
   shows an editable "Bonus Slots" input that adds to the calculated max slots
   (10 + Might×2 + bonus)

 - Replace single Enhancement <select> in spell cast dialog with a checkbox
   list; multiple enhancements can now be selected simultaneously — stress
   costs, pool penalties, and boolean flags (redDice, noStress) are aggregated
   across all active enhancements

 - Include skills.magic.modifier in basePool for both spell and miracle dialogs
   and in baseDice in rollSpellCast / rollMiracleCast; modifier is shown in
   the dialog pool-info line and in the chat card when non-zero

 - Fix: pool-reduction indicator in rollSpellCast now compares against
   intRank + magicRank + magicMod (was missing magicMod)

module/applications/miracle-dialog.mjs

@@ -8,8 +8,10 @@ export default class OathHammerMiracleDialog {
 
     const wpRank       = actorSys.attributes.willpower.rank
     const magicRank    = actorSys.skills.magic.rank
+    const magicMod     = actorSys.skills.magic.modifier ?? 0
     const magicColor   = actorSys.skills.magic.colorDiceType ?? "white"
-    const basePool     = wpRank + magicRank
+    const basePool     = wpRank + magicRank + magicMod
+    const magicModDisplay = magicMod > 0 ? `+${magicMod}` : magicMod < 0 ? `${magicMod}` : ""
 
     const isRitual = sys.isRitual
     const dv       = isRitual ? (sys.difficultyValue || 1) : null
@@ -60,6 +62,8 @@ export default class OathHammerMiracleDialog {
       spellSave:     sys.spellSave,
       wpRank,
       magicRank,
+      magicMod,
+      magicModDisplay,
       basePool,
       miracleCountOptions,
       colorOptions,