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/BossPanel.tsx

@@ -10,6 +10,7 @@ interface BossCardProps {
   prestigeCount: number;
   onChallenge: (bossId: string) => void;
   isChallenging: boolean;
+  unlockHint?: string | undefined;
 }
 
 const BossCard = ({
@@ -17,6 +18,7 @@ const BossCard = ({
   prestigeCount,
   onChallenge,
   isChallenging,
+  unlockHint,
 }: BossCardProps): React.JSX.Element => {
   const hpPercent = (boss.currentHp / boss.maxHp) * 100;
   const isPrestigeLocked = boss.prestigeRequirement > prestigeCount;
@@ -33,6 +35,9 @@ const BossCard = ({
             🔒 Requires Prestige {boss.prestigeRequirement}
           </p>
         )}
+        {!isPrestigeLocked && boss.status === "locked" && unlockHint && (
+          <p className="unlock-hint">{unlockHint}</p>
+        )}
       </div>
 
       {boss.status !== "locked" && boss.status !== "defeated" && (
@@ -146,6 +151,26 @@ export const BossPanel = (): React.JSX.Element => {
     ? zoneBosses
     : zoneBosses.filter((b) => b.status !== "locked");
 
+  const bossUnlockHints = new Map<string, string>();
+  for (const zone of zones) {
+    const allZoneBosses = state.bosses.filter((b) => b.zoneId === zone.id);
+    for (let i = 0; i < allZoneBosses.length; i++) {
+      const boss = allZoneBosses[i];
+      if (!boss || boss.status !== "locked") continue;
+      if (i === 0 && zone.unlockBossId) {
+        const gateBoss = state.bosses.find((b) => b.id === zone.unlockBossId);
+        if (gateBoss) {
+          bossUnlockHints.set(boss.id, `⚔️ Defeat: ${gateBoss.name}`);
+        }
+      } else if (i > 0) {
+        const prevBoss = allZoneBosses[i - 1];
+        if (prevBoss) {
+          bossUnlockHints.set(boss.id, `⚔️ Defeat: ${prevBoss.name} first`);
+        }
+      }
+    }
+  }
+
   return (
     <section className="panel boss-panel">
       <div className="panel-header">
@@ -181,6 +206,7 @@ export const BossPanel = (): React.JSX.Element => {
             boss={boss}
             isChallenging={challengingBossId === boss.id}
             prestigeCount={state.prestige.count}
+            unlockHint={bossUnlockHints.get(boss.id)}
             onChallenge={(id) => {
               void handleChallenge(id);
             }}