feat(metadata): SQLite backend, storage reconciliation and local defaults

- pluggable per-domain Repository interfaces; PostgreSQL and SQLite impls
- SQLite on modernc.org/sqlite (WAL, busy_timeout, foreign_keys, immediate tx)
- separate migrations/sqlite and db.MigrateSQLite; store.NewPostgres/NewSQLite
- cmd/reconcile compares object storage with the journal (report, then --delete)
- storage.Backend.List and photos.Repository.AllStorageKeys
- DB_BACKEND/SQLITE_PATH and STORAGE_BACKEND/FS_ROOT selectable; local defaults
  (sqlite ./galo.db, fs ./data)
- Makefile reconcile/reconcile-delete; docs and .env.example updated

backend/internal/members/sqlite_store.go

@@ -0,0 +1,133 @@
+package members
+
+import (
+	"context"
+	"database/sql"
+	"errors"
+
+	"shared-album/internal/models"
+	"shared-album/internal/sqliteutil"
+)
+
+// SQLiteStore is the SQLite implementation of Repository.
+type SQLiteStore struct {
+	db *sql.DB
+}
+
+func NewSQLiteStore(db *sql.DB) *SQLiteStore { return &SQLiteStore{db: db} }
+
+func (s *SQLiteStore) Role(ctx context.Context, albumID, userID string) (string, error) {
+	var role string
+	err := s.db.QueryRowContext(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, sql.ErrNoRows) {
+			return "", nil
+		}
+		return "", err
+	}
+	return role, nil
+}
+
+func (s *SQLiteStore) List(ctx context.Context, albumID string) ([]models.AlbumMember, error) {
+	rows, err := s.db.QueryContext(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
+		var invitedBy sql.NullString
+		var joinedAt string
+		if err := rows.Scan(&m.AlbumID, &m.UserID, &m.Role, &invitedBy, &joinedAt,
+			&m.User.ID, &m.User.Email, &m.User.Name, &m.User.AvatarURL); err != nil {
+			return nil, err
+		}
+		if invitedBy.Valid {
+			m.InvitedBy = &invitedBy.String
+		}
+		m.JoinedAt = sqliteutil.ParseTime(joinedAt)
+		out = append(out, m)
+	}
+	return out, rows.Err()
+}
+
+func (s *SQLiteStore) Add(ctx context.Context, albumID, userID, role string, invitedBy *string) error {
+	_, err := s.db.ExecContext(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 *SQLiteStore) UpdateRole(ctx context.Context, albumID, userID, role string) error {
+	res, err := s.db.ExecContext(ctx,
+		`UPDATE album_members SET role = $3 WHERE album_id = $1 AND user_id = $2`,
+		albumID, userID, role)
+	if err != nil {
+		return err
+	}
+	if n, _ := res.RowsAffected(); n == 0 {
+		return ErrNotFound
+	}
+	return nil
+}
+
+func (s *SQLiteStore) Remove(ctx context.Context, albumID, userID string) error {
+	res, err := s.db.ExecContext(ctx,
+		`DELETE FROM album_members WHERE album_id = $1 AND user_id = $2`, albumID, userID)
+	if err != nil {
+		return err
+	}
+	if n, _ := res.RowsAffected(); n == 0 {
+		return ErrNotFound
+	}
+	return nil
+}
+
+func (s *SQLiteStore) CreateInvite(ctx context.Context, inv *models.Invite) error {
+	var createdAt string
+	err := s.db.QueryRowContext(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, sqliteutil.FormatTime(inv.ExpiresAt), inv.MaxUses,
+	).Scan(&createdAt)
+	if err != nil {
+		return err
+	}
+	inv.CreatedAt = sqliteutil.ParseTime(createdAt)
+	return nil
+}
+
+func (s *SQLiteStore) GetInviteByToken(ctx context.Context, token string) (*models.Invite, error) {
+	var inv models.Invite
+	var expiresAt, createdAt string
+	err := s.db.QueryRowContext(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, &expiresAt, &inv.MaxUses, &inv.Uses, &createdAt)
+	if err != nil {
+		if errors.Is(err, sql.ErrNoRows) {
+			return nil, ErrNotFound
+		}
+		return nil, err
+	}
+	inv.ExpiresAt = sqliteutil.ParseTime(expiresAt)
+	inv.CreatedAt = sqliteutil.ParseTime(createdAt)
+	return &inv, nil
+}
+
+func (s *SQLiteStore) IncrementUses(ctx context.Context, id string) error {
+	_, err := s.db.ExecContext(ctx, `UPDATE invites SET uses = uses + 1 WHERE id = $1`, id)
+	return err
+}