feat: sequential zone unlocking with dual boss+quest gate conditions

Zones now unlock in strict linear order. Each zone requires both the
final boss AND the final quest of the previous zone to be completed:

Verdant Vale → Shattered Ruins (forest_giant + ancient_ruins)
Shattered Ruins → Frozen Peaks (elder_dragon + dragon_lair)
Frozen Peaks → Shadow Marshes (void_titan + storm_citadel)
Shadow Marshes → Volcanic Depths (mud_kraken + plague_ruins)
Volcanic Depths → Astral Void (phoenix_lord + the_forge)

- Zone type gains `unlockQuestId` field alongside `unlockBossId`
- boss.ts checks both conditions before unlocking zone on boss defeat
- tick.ts checks both conditions and unlocks zones + first boss on
  quest completion if the boss condition is already met
- GameContext optimistic update also respects dual-condition logic
- BossPanel zone-gate hints now show both "⚔️ Defeat: X & 📜 Complete: Y"
- game.ts backfill syncs unlockQuestId and re-verifies zone status
  using both conditions, reverting incorrectly-unlocked saves

apps/web/src/context/GameContext.tsx

@@ -279,7 +279,14 @@ export const GameProvider = ({ children }: { children: React.ReactNode }): React
           const nextZoneBossId = zoneBosses[zoneIdx + 1]?.id;
 
           // Find newly unlocked zones and their first bosses
-          const newlyUnlockedZones = (prev.zones ?? []).filter((z) => z.unlockBossId === bossId && z.status === "locked");
+          // A zone unlocks when BOTH the gate boss is defeated AND the gate quest is completed
+          const newlyUnlockedZones = (prev.zones ?? []).filter((z) => {
+            if (z.status !== "locked" || z.unlockBossId !== bossId) return false;
+            const questOk =
+              z.unlockQuestId == null ||
+              prev.quests.some((q) => q.id === z.unlockQuestId && q.status === "completed");
+            return questOk;
+          });
           const newZoneFirstBossIds = newlyUnlockedZones.map((z) => {
             const firstBoss = prev.bosses.find((b) => b.zoneId === z.id);
             return firstBoss?.id;
@@ -297,9 +304,13 @@ export const GameProvider = ({ children }: { children: React.ReactNode }): React
               }
               return b;
             }),
-            zones: (prev.zones ?? []).map((z) =>
-              z.unlockBossId === bossId ? { ...z, status: "unlocked" as const } : z,
-            ),
+            zones: (prev.zones ?? []).map((z) => {
+              if (z.status !== "locked" || z.unlockBossId !== bossId) return z;
+              const questOk =
+                z.unlockQuestId == null ||
+                prev.quests.some((q) => q.id === z.unlockQuestId && q.status === "completed");
+              return questOk ? { ...z, status: "unlocked" as const } : z;
+            }),
             resources: result.rewards
               ? {
                   ...prev.resources,