feat: add image upload for avatar and banner

.env.example

@@ -24,5 +24,21 @@ RUST_ENV=development      # set to "production" to disable AP debug mode
 # but events will not be delivered to the worker)
 # NATS_URL=nats://localhost:4222
 
+# Media storage — local filesystem (default) or S3/MinIO
+STORAGE_BACKEND=local
+STORAGE_PATH=./media            # required when STORAGE_BACKEND=local
+# STORAGE_PREFIX=               # optional key prefix
+
+# S3/MinIO (set STORAGE_BACKEND=s3 to use)
+# S3_ENDPOINT=http://localhost:9000
+# S3_ACCESS_KEY_ID=minioadmin
+# S3_SECRET_ACCESS_KEY=minioadmin
+# S3_BUCKET=thoughts
+# S3_REGION=us-east-1
+
+# Upload limits (optional, defaults shown)
+# UPLOAD_MAX_BYTES=5242880
+# UPLOAD_ALLOWED_TYPES=image/jpeg,image/png,image/gif,image/webp,image/avif
+
 # Logging
 RUST_LOG=info