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/sharelinks/sqlite_store.go

@@ -0,0 +1,90 @@
+package sharelinks
+
+import (
+	"context"
+	"database/sql"
+	"errors"
+	"time"
+
+	"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) Create(ctx context.Context, l *models.ShareLink) error {
+	var createdAt string
+	err := s.db.QueryRowContext(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, sqliteutil.FormatTime(l.ExpiresAt),
+	).Scan(&createdAt)
+	if err != nil {
+		return err
+	}
+	l.CreatedAt = sqliteutil.ParseTime(createdAt)
+	return nil
+}
+
+func (s *SQLiteStore) ListByAlbum(ctx context.Context, albumID string) ([]models.ShareLink, error) {
+	rows, err := s.db.QueryContext(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
+		var createdAt, expiresAt string
+		var revokedAt sql.NullString
+		if err := rows.Scan(&l.ID, &l.AlbumID, &l.Token, &l.CreatedBy, &createdAt, &expiresAt, &revokedAt); err != nil {
+			return nil, err
+		}
+		l.CreatedAt = sqliteutil.ParseTime(createdAt)
+		l.ExpiresAt = sqliteutil.ParseTime(expiresAt)
+		l.RevokedAt = sqliteutil.ParseNullTime(revokedAt)
+		out = append(out, l)
+	}
+	return out, rows.Err()
+}
+
+func (s *SQLiteStore) GetByToken(ctx context.Context, token string) (*models.ShareLink, error) {
+	var l models.ShareLink
+	var createdAt, expiresAt string
+	var revokedAt sql.NullString
+	err := s.db.QueryRowContext(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, &createdAt, &expiresAt, &revokedAt)
+	if err != nil {
+		if errors.Is(err, sql.ErrNoRows) {
+			return nil, ErrNotFound
+		}
+		return nil, err
+	}
+	l.CreatedAt = sqliteutil.ParseTime(createdAt)
+	l.ExpiresAt = sqliteutil.ParseTime(expiresAt)
+	l.RevokedAt = sqliteutil.ParseNullTime(revokedAt)
+	return &l, nil
+}
+
+func (s *SQLiteStore) Revoke(ctx context.Context, id, albumID string) error {
+	res, err := s.db.ExecContext(ctx,
+		`UPDATE share_links SET revoked_at = $3 WHERE id = $1 AND album_id = $2 AND revoked_at IS NULL`,
+		id, albumID, sqliteutil.FormatTime(time.Now()))
+	if err != nil {
+		return err
+	}
+	if n, _ := res.RowsAffected(); n == 0 {
+		return ErrNotFound
+	}
+	return nil
+}