feat: achievement system with 10 unlockable achievements

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

store/achievements.go

@@ -0,0 +1,72 @@
+package store
+
+import (
+	bolt "go.etcd.io/bbolt"
+)
+
+var bucketAchievements = []byte("achievements")
+
+type Achievement struct {
+	ID          string `json:"id"`
+	Name        string `json:"name"`
+	Description string `json:"description"`
+	Unlocked    bool   `json:"unlocked"`
+}
+
+var AchievementDefs = []Achievement{
+	{ID: "first_clear", Name: "Dungeon Delver", Description: "Clear floor 5 for the first time"},
+	{ID: "boss_slayer", Name: "Boss Slayer", Description: "Defeat any boss"},
+	{ID: "floor10", Name: "Deep Explorer", Description: "Reach floor 10"},
+	{ID: "floor20", Name: "Conqueror", Description: "Conquer the Catacombs (floor 20)"},
+	{ID: "solo_clear", Name: "Lone Wolf", Description: "Clear floor 5 solo"},
+	{ID: "gold_hoarder", Name: "Gold Hoarder", Description: "Accumulate 200+ gold in one run"},
+	{ID: "no_death", Name: "Untouchable", Description: "Complete a floor without anyone dying"},
+	{ID: "full_party", Name: "Fellowship", Description: "Start a game with 4 players"},
+	{ID: "relic_collector", Name: "Relic Collector", Description: "Collect 3+ relics in one run"},
+	{ID: "flee_master", Name: "Tactical Retreat", Description: "Successfully flee from combat"},
+}
+
+func (d *DB) initAchievements() error {
+	return d.db.Update(func(tx *bolt.Tx) error {
+		_, err := tx.CreateBucketIfNotExists(bucketAchievements)
+		return err
+	})
+}
+
+func (d *DB) UnlockAchievement(player, achievementID string) (bool, error) {
+	key := []byte(player + ":" + achievementID)
+	alreadyUnlocked := false
+	err := d.db.Update(func(tx *bolt.Tx) error {
+		b := tx.Bucket(bucketAchievements)
+		if b.Get(key) != nil {
+			alreadyUnlocked = true
+			return nil
+		}
+		return b.Put(key, []byte("1"))
+	})
+	// Returns true if newly unlocked (not already had it)
+	return !alreadyUnlocked, err
+}
+
+func (d *DB) GetAchievements(player string) ([]Achievement, error) {
+	unlocked := make(map[string]bool)
+	err := d.db.View(func(tx *bolt.Tx) error {
+		b := tx.Bucket(bucketAchievements)
+		if b == nil {
+			return nil
+		}
+		for _, a := range AchievementDefs {
+			key := []byte(player + ":" + a.ID)
+			if b.Get(key) != nil {
+				unlocked[a.ID] = true
+			}
+		}
+		return nil
+	})
+	result := make([]Achievement, len(AchievementDefs))
+	for i, a := range AchievementDefs {
+		result[i] = a
+		result[i].Unlocked = unlocked[a.ID]
+	}
+	return result, err
+}