feat: replace fs scans with bbolt for fast, persistent metadata management

Signed-off-by: skidoodle <contact@albert.lol>

internal/app/db.go

@@ -0,0 +1,35 @@
+package app
+
+import (
+	"path/filepath"
+	"time"
+
+	"go.etcd.io/bbolt"
+)
+
+type FileMeta struct {
+	ID        string    `json:"id"`
+	Size      int64     `json:"size"`
+	CreatedAt time.Time `json:"created_at"`
+	ExpiresAt time.Time `json:"expires_at"`
+}
+
+func InitDB(storageDir string) (*bbolt.DB, error) {
+	path := filepath.Join(storageDir, DBFileName)
+	db, err := bbolt.Open(path, 0600, &bbolt.Options{Timeout: 1 * time.Second})
+	if err != nil {
+		return nil, err
+	}
+
+	err = db.Update(func(tx *bbolt.Tx) error {
+		_, err := tx.CreateBucketIfNotExists([]byte(DBBucketName))
+		return err
+	})
+
+	if err != nil {
+		db.Close()
+		return nil, err
+	}
+
+	return db, nil
+}