Add MapLibre demo and route uploads through backend.

This introduces a MapLibre GL + Three.js web demo for object placement and sharing, and changes asset upload flow to use backend upload endpoints so clients no longer receive direct MinIO URLs.

Made-with: Cursor

internal/storage/s3_signer.go

@@ -3,6 +3,7 @@ package storage
 import (
 	"context"
 	"errors"
+	"io"
 	"time"
 
 	"github.com/minio/minio-go/v7"
@@ -47,14 +48,6 @@ func bucketLookup(pathStyle bool) minio.BucketLookupType {
 	return minio.BucketLookupAuto
 }
 
-func (s *S3Signer) SignedPutObjectURL(ctx context.Context, objectKey string, expiry time.Duration, _ string) (string, error) {
-	u, err := s.client.PresignedPutObject(ctx, s.bucket, objectKey, expiry)
-	if err != nil {
-		return "", err
-	}
-	return u.String(), nil
-}
-
 func (s *S3Signer) SignedGetObjectURL(ctx context.Context, objectKey string, expiry time.Duration) (string, error) {
 	u, err := s.client.PresignedGetObject(ctx, s.bucket, objectKey, expiry, nil)
 	if err != nil {
@@ -62,3 +55,10 @@ func (s *S3Signer) SignedGetObjectURL(ctx context.Context, objectKey string, exp
 	}
 	return u.String(), nil
 }
+
+func (s *S3Signer) PutObject(ctx context.Context, objectKey, contentType string, body io.Reader, size int64) error {
+	_, err := s.client.PutObject(ctx, s.bucket, objectKey, body, size, minio.PutObjectOptions{
+		ContentType: contentType,
+	})
+	return err
+}