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/auth/repository.go

@@ -0,0 +1,19 @@
+package auth
+
+import (
+	"context"
+
+	"shared-album/internal/models"
+)
+
+// Repository is the persistence contract for the auth domain.
+type Repository interface {
+	CreateUser(ctx context.Context, u *models.User) error
+	GetUserByEmail(ctx context.Context, email string) (*models.User, error)
+	GetUserByID(ctx context.Context, id string) (*models.User, error)
+	UpdatePreferences(ctx context.Context, userID string, raw []byte) error
+	CreateRefreshToken(ctx context.Context, t *models.RefreshToken) error
+	GetRefreshToken(ctx context.Context, hash string) (*models.RefreshToken, error)
+	RevokeRefreshToken(ctx context.Context, id string) error
+	RevokeAllUserTokens(ctx context.Context, userID string) error
+}

backend/internal/auth/service.go

@@ -18,11 +18,11 @@ type TokenPair struct {
 }
 
 type Service struct {
-	store *Store
+	store Repository
 	tm    *TokenManager
 }
 
-func NewService(store *Store, tm *TokenManager) *Service {
+func NewService(store Repository, tm *TokenManager) *Service {
 	return &Service{store: store, tm: tm}
 }
 

backend/internal/auth/sqlite_store.go

@@ -0,0 +1,111 @@
+package auth
+
+import (
+	"context"
+	"database/sql"
+	"encoding/json"
+	"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) CreateUser(ctx context.Context, u *models.User) error {
+	_, err := s.db.ExecContext(ctx,
+		`INSERT INTO users (id, email, password_hash, name, avatar_url)
+		 VALUES ($1, $2, $3, $4, $5)`,
+		u.ID, u.Email, u.PasswordHash, u.Name, nullIfEmpty(u.AvatarURL))
+	return err
+}
+
+func (s *SQLiteStore) GetUserByEmail(ctx context.Context, email string) (*models.User, error) {
+	return s.scanUser(s.db.QueryRowContext(ctx,
+		`SELECT id, email, password_hash, name, COALESCE(avatar_url, ''),
+		        COALESCE(preferences, '{}'), created_at
+		 FROM users WHERE lower(email) = lower($1)`, email))
+}
+
+func (s *SQLiteStore) GetUserByID(ctx context.Context, id string) (*models.User, error) {
+	return s.scanUser(s.db.QueryRowContext(ctx,
+		`SELECT id, email, password_hash, name, COALESCE(avatar_url, ''),
+		        COALESCE(preferences, '{}'), created_at
+		 FROM users WHERE id = $1`, id))
+}
+
+func (s *SQLiteStore) scanUser(row *sql.Row) (*models.User, error) {
+	var u models.User
+	var prefs, createdAt string
+	if err := row.Scan(&u.ID, &u.Email, &u.PasswordHash, &u.Name, &u.AvatarURL, &prefs, &createdAt); err != nil {
+		if errors.Is(err, sql.ErrNoRows) {
+			return nil, ErrNotFound
+		}
+		return nil, err
+	}
+	u.CreatedAt = sqliteutil.ParseTime(createdAt)
+	if prefs != "" && prefs != "null" {
+		_ = json.Unmarshal([]byte(prefs), &u.Preferences)
+	}
+	return &u, nil
+}
+
+func (s *SQLiteStore) UpdatePreferences(ctx context.Context, userID string, raw []byte) error {
+	res, err := s.db.ExecContext(ctx,
+		`UPDATE users SET preferences = $2 WHERE id = $1`, userID, string(raw))
+	if err != nil {
+		return err
+	}
+	if n, _ := res.RowsAffected(); n == 0 {
+		return ErrNotFound
+	}
+	return nil
+}
+
+func (s *SQLiteStore) CreateRefreshToken(ctx context.Context, t *models.RefreshToken) error {
+	_, err := s.db.ExecContext(ctx,
+		`INSERT INTO refresh_tokens (id, user_id, token_hash, expires_at)
+		 VALUES ($1, $2, $3, $4)`,
+		t.ID, t.UserID, t.TokenHash, sqliteutil.FormatTime(t.ExpiresAt))
+	return err
+}
+
+func (s *SQLiteStore) GetRefreshToken(ctx context.Context, hash string) (*models.RefreshToken, error) {
+	var t models.RefreshToken
+	var expiresAt, createdAt string
+	var revokedAt sql.NullString
+	err := s.db.QueryRowContext(ctx,
+		`SELECT id, user_id, token_hash, expires_at, revoked_at, created_at
+		 FROM refresh_tokens WHERE token_hash = $1`, hash).
+		Scan(&t.ID, &t.UserID, &t.TokenHash, &expiresAt, &revokedAt, &createdAt)
+	if err != nil {
+		if errors.Is(err, sql.ErrNoRows) {
+			return nil, ErrNotFound
+		}
+		return nil, err
+	}
+	t.ExpiresAt = sqliteutil.ParseTime(expiresAt)
+	t.CreatedAt = sqliteutil.ParseTime(createdAt)
+	t.RevokedAt = sqliteutil.ParseNullTime(revokedAt)
+	return &t, nil
+}
+
+func (s *SQLiteStore) RevokeRefreshToken(ctx context.Context, id string) error {
+	_, err := s.db.ExecContext(ctx,
+		`UPDATE refresh_tokens SET revoked_at = $2 WHERE id = $1 AND revoked_at IS NULL`,
+		id, sqliteutil.FormatTime(time.Now()))
+	return err
+}
+
+func (s *SQLiteStore) RevokeAllUserTokens(ctx context.Context, userID string) error {
+	_, err := s.db.ExecContext(ctx,
+		`UPDATE refresh_tokens SET revoked_at = $2 WHERE user_id = $1 AND revoked_at IS NULL`,
+		userID, sqliteutil.FormatTime(time.Now()))
+	return err
+}