Add S3 configuration and presigned URL logic for file upload and download

app/etc/blog.yaml

@@ -1,3 +1,14 @@
 Name: Blog
 Host: 0.0.0.0
 Port: 8888
+
+Database:
+  DSN: "${DATABASE_DSN}" # postgres: host=localhost port=5432 user=postgres password=your_password dbname=steam_union sslmode=disable
+
+S3:
+  Region: us-east-1
+  Bucket: your-bucket-name
+  AccessKeyID: your-access-key-id
+  SecretAccessKey: your-secret-access-key
+  Endpoint: # Optional: for custom S3-compatible endpoints (e.g., MinIO)
+  PresignedURLExpiration: 3600 # Expiration time in seconds (default 1 hour)