feat: implement shared-album multi-user photo album

Backend (Go/Gin/pgx): env config, pgx pool with retries, Garage S3 client
(path-style, region garage), embedded golang-migrate migrations, JWT auth with
refresh rotation, albums CRUD, members/roles/invites with no-escalation matrix,
photo upload + async imaging/goexif WebP variants, cursor pagination, presigned
URLs, likes/comments, SSE hub (album + personal), notifications, share links.

Frontend (SvelteKit 2 + Svelte 5 + Tailwind v4): API wrapper with 401 refresh,
auth store, all screens, Uploader/PhotoGrid/Lightbox/Comments, SSE client with
reconnect + REST catch-up, three themes + system via data-theme.

Deploy without Docker: Makefile builds the frontend into backend/static and
embeds it (go:embed) into a single statically linked binary; systemd unit and
nginx SSE example included.

Use gen2brain/webp (-tags nodynamic) instead of cgo kolesa-team/go-webp to keep
CGO_ENABLED=0 static builds; design.md/proposal.md updated accordingly.

backend/internal/sharelinks/store.go

@@ -0,0 +1,76 @@
+package sharelinks
+
+import (
+	"context"
+	"errors"
+
+	"github.com/jackc/pgx/v5"
+	"github.com/jackc/pgx/v5/pgxpool"
+
+	"shared-album/internal/models"
+)
+
+var ErrNotFound = errors.New("not found")
+
+type Store struct {
+	pool *pgxpool.Pool
+}
+
+func NewStore(pool *pgxpool.Pool) *Store { return &Store{pool: pool} }
+
+func (s *Store) Create(ctx context.Context, l *models.ShareLink) error {
+	return s.pool.QueryRow(ctx,
+		`INSERT INTO share_links (id, album_id, token, created_by, expires_at)
+		 VALUES ($1, $2, $3, $4, $5)
+		 RETURNING created_at`,
+		l.ID, l.AlbumID, l.Token, l.CreatedBy, l.ExpiresAt,
+	).Scan(&l.CreatedAt)
+}
+
+func (s *Store) ListByAlbum(ctx context.Context, albumID string) ([]models.ShareLink, error) {
+	rows, err := s.pool.Query(ctx,
+		`SELECT id, album_id, token, created_by, created_at, expires_at, revoked_at
+		 FROM share_links WHERE album_id = $1 ORDER BY created_at DESC`, albumID)
+	if err != nil {
+		return nil, err
+	}
+	defer rows.Close()
+
+	out := []models.ShareLink{}
+	for rows.Next() {
+		var l models.ShareLink
+		if err := rows.Scan(&l.ID, &l.AlbumID, &l.Token, &l.CreatedBy, &l.CreatedAt, &l.ExpiresAt, &l.RevokedAt); err != nil {
+			return nil, err
+		}
+		out = append(out, l)
+	}
+	return out, rows.Err()
+}
+
+func (s *Store) GetByToken(ctx context.Context, token string) (*models.ShareLink, error) {
+	var l models.ShareLink
+	err := s.pool.QueryRow(ctx,
+		`SELECT id, album_id, token, created_by, created_at, expires_at, revoked_at
+		 FROM share_links WHERE token = $1`, token).
+		Scan(&l.ID, &l.AlbumID, &l.Token, &l.CreatedBy, &l.CreatedAt, &l.ExpiresAt, &l.RevokedAt)
+	if err != nil {
+		if errors.Is(err, pgx.ErrNoRows) {
+			return nil, ErrNotFound
+		}
+		return nil, err
+	}
+	return &l, nil
+}
+
+func (s *Store) Revoke(ctx context.Context, id, albumID string) error {
+	tag, err := s.pool.Exec(ctx,
+		`UPDATE share_links SET revoked_at = now() WHERE id = $1 AND album_id = $2 AND revoked_at IS NULL`,
+		id, albumID)
+	if err != nil {
+		return err
+	}
+	if tag.RowsAffected() == 0 {
+		return ErrNotFound
+	}
+	return nil
+}