Add photo galleries API and frontend for public and admin viewing.

Introduces the Go photo-api service, nginx/systemd deploy wiring, and Next.js gallery/lightbox pages so event photos can be managed and browsed.

Co-authored-by: Cursor <cursoragent@cursor.com>

photo-api/internal/storage/storage.go

@@ -0,0 +1,32 @@
+// Package storage abstracts photo object storage. Selection follows the
+// backend's convention (backend/src/lib/storage.ts): S3 when S3_ENDPOINT
+// and S3_BUCKET are both set, local disk otherwise. Keys are identical on
+// both backends: galleries/<galleryID>/<variantDir>/<photoID>.<ext>.
+package storage
+
+import (
+	"context"
+	"errors"
+	"io"
+	"time"
+
+	"git.azzamo.net/Michilis/Spanglish/photo-api/internal/config"
+)
+
+// ErrNoPresign is returned by backends that cannot presign (local disk);
+// callers then stream the object through the API instead.
+var ErrNoPresign = errors.New("presigned URLs not supported")
+
+type Storage interface {
+	Put(ctx context.Context, key string, r io.Reader, size int64, contentType string) error
+	Open(ctx context.Context, key string) (io.ReadCloser, int64, error)
+	Delete(ctx context.Context, key string) error
+	PresignGet(ctx context.Context, key, downloadFilename, contentType string, expiry time.Duration) (string, error)
+}
+
+func New(cfg config.Config) (Storage, error) {
+	if cfg.S3Enabled() {
+		return newS3(cfg)
+	}
+	return newLocal(cfg.StoragePath)
+}