feat: display unlock conditions on all locked items

All locked items now show players exactly what they need to do next:
- Adventurers: "📜 Complete: [Quest Name]"
- Upgrades: "⚔️ Defeat: [Boss]" or "📜 Complete: [Quest]"
- Equipment (boss drops): "⚔️ Drop: [Boss Name]" instead of generic label
- Bosses: "⚔️ Defeat: [Previous Boss] first" or zone gate boss
- Quests: "📜 Complete: [Prerequisite Quest]"

Also wires adventurer unlocks through quests (militia through dragon_rider
had no unlock path), retroactively applies rewards on existing saves,
syncs boss reward arrays from defaults on load, and removes invalid
rune_stone reference from Forest Giant.

apps/web/src/components/game/EquipmentPanel.tsx

@@ -35,6 +35,7 @@ interface EquipmentCardProps {
   gold: number;
   essence: number;
   crystals: number;
+  dropBossName?: string | undefined;
 }
 
 const costLabel = (cost: { gold: number; essence: number; crystals: number }): string => {
@@ -45,7 +46,7 @@ const costLabel = (cost: { gold: number; essence: number; crystals: number }): s
   return parts.join("  ");
 };
 
-const EquipmentCard = ({ item, gold, essence, crystals }: EquipmentCardProps): React.JSX.Element => {
+const EquipmentCard = ({ item, gold, essence, crystals, dropBossName }: EquipmentCardProps): React.JSX.Element => {
   const { equipItem, buyEquipment } = useGame();
 
   const canAfford = item.cost
@@ -67,7 +68,11 @@ const EquipmentCard = ({ item, gold, essence, crystals }: EquipmentCardProps): R
         )}
       </div>
       <div className="equipment-action">
-        {!item.owned && !item.cost && <span className="equipment-locked">🔒 Boss drop</span>}
+        {!item.owned && !item.cost && (
+          <span className="equipment-locked">
+            {dropBossName ? `⚔️ Drop: ${dropBossName}` : "🔒 Boss drop"}
+          </span>
+        )}
         {!item.owned && item.cost && (
           <button
             className="equip-button"
@@ -109,6 +114,13 @@ export const EquipmentPanel = (): React.JSX.Element => {
   const equipment = state.equipment ?? [];
   const unownedCount = equipment.filter((e) => !e.owned).length;
 
+  const equipmentDropSources = new Map<string, string>();
+  for (const boss of state.bosses) {
+    for (const equipmentId of (boss.equipmentRewards ?? [])) {
+      equipmentDropSources.set(equipmentId, boss.name);
+    }
+  }
+
   return (
     <section className="panel equipment-panel">
       <div className="panel-header">
@@ -138,6 +150,7 @@ export const EquipmentPanel = (): React.JSX.Element => {
                   gold={state.resources.gold}
                   essence={state.resources.essence}
                   crystals={state.resources.crystals}
+                  dropBossName={equipmentDropSources.get(item.id)}
                 />
               ))}
               {items.length === 0 && (