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/members/store.go

@@ -0,0 +1,121 @@
+package members
+
+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) Role(ctx context.Context, albumID, userID string) (string, error) {
+	var role string
+	err := s.pool.QueryRow(ctx,
+		`SELECT role FROM album_members WHERE album_id = $1 AND user_id = $2`,
+		albumID, userID).Scan(&role)
+	if err != nil {
+		if errors.Is(err, pgx.ErrNoRows) {
+			return "", nil
+		}
+		return "", err
+	}
+	return role, nil
+}
+
+func (s *Store) List(ctx context.Context, albumID string) ([]models.AlbumMember, error) {
+	rows, err := s.pool.Query(ctx,
+		`SELECT m.album_id, m.user_id, m.role, m.invited_by, m.joined_at,
+		        u.id, u.email, u.name, COALESCE(u.avatar_url, '')
+		 FROM album_members m
+		 JOIN users u ON u.id = m.user_id
+		 WHERE m.album_id = $1
+		 ORDER BY m.joined_at`, albumID)
+	if err != nil {
+		return nil, err
+	}
+	defer rows.Close()
+
+	out := []models.AlbumMember{}
+	for rows.Next() {
+		var m models.AlbumMember
+		if err := rows.Scan(&m.AlbumID, &m.UserID, &m.Role, &m.InvitedBy, &m.JoinedAt,
+			&m.User.ID, &m.User.Email, &m.User.Name, &m.User.AvatarURL); err != nil {
+			return nil, err
+		}
+		out = append(out, m)
+	}
+	return out, rows.Err()
+}
+
+func (s *Store) Add(ctx context.Context, albumID, userID, role string, invitedBy *string) error {
+	_, err := s.pool.Exec(ctx,
+		`INSERT INTO album_members (album_id, user_id, role, invited_by)
+		 VALUES ($1, $2, $3, $4)
+		 ON CONFLICT (album_id, user_id) DO UPDATE SET role = EXCLUDED.role`,
+		albumID, userID, role, invitedBy)
+	return err
+}
+
+func (s *Store) UpdateRole(ctx context.Context, albumID, userID, role string) error {
+	tag, err := s.pool.Exec(ctx,
+		`UPDATE album_members SET role = $3 WHERE album_id = $1 AND user_id = $2`,
+		albumID, userID, role)
+	if err != nil {
+		return err
+	}
+	if tag.RowsAffected() == 0 {
+		return ErrNotFound
+	}
+	return nil
+}
+
+func (s *Store) Remove(ctx context.Context, albumID, userID string) error {
+	tag, err := s.pool.Exec(ctx,
+		`DELETE FROM album_members WHERE album_id = $1 AND user_id = $2`, albumID, userID)
+	if err != nil {
+		return err
+	}
+	if tag.RowsAffected() == 0 {
+		return ErrNotFound
+	}
+	return nil
+}
+
+func (s *Store) CreateInvite(ctx context.Context, inv *models.Invite) error {
+	return s.pool.QueryRow(ctx,
+		`INSERT INTO invites (id, album_id, token, role, created_by, expires_at, max_uses)
+		 VALUES ($1, $2, $3, $4, $5, $6, $7)
+		 RETURNING created_at`,
+		inv.ID, inv.AlbumID, inv.Token, inv.Role, inv.CreatedBy, inv.ExpiresAt, inv.MaxUses,
+	).Scan(&inv.CreatedAt)
+}
+
+func (s *Store) GetInviteByToken(ctx context.Context, token string) (*models.Invite, error) {
+	var inv models.Invite
+	err := s.pool.QueryRow(ctx,
+		`SELECT id, album_id, token, role, created_by, expires_at, max_uses, uses, created_at
+		 FROM invites WHERE token = $1`, token).
+		Scan(&inv.ID, &inv.AlbumID, &inv.Token, &inv.Role, &inv.CreatedBy, &inv.ExpiresAt, &inv.MaxUses, &inv.Uses, &inv.CreatedAt)
+	if err != nil {
+		if errors.Is(err, pgx.ErrNoRows) {
+			return nil, ErrNotFound
+		}
+		return nil, err
+	}
+	return &inv, nil
+}
+
+func (s *Store) IncrementUses(ctx context.Context, id string) error {
+	_, err := s.pool.Exec(ctx, `UPDATE invites SET uses = uses + 1 WHERE id = $1`, id)
+	return err
+}