feat(PROJ-44): ocr_chars-Spalte + SetOCRResult-Helper

DB-Schema bekommt eine idempotente ocr_chars BIGINT-Spalte (Default 0).
SetOCRResult schreibt status und chars atomar; GetOCRMeta liest beide
mit COALESCE-Defaults. Der OCR-Worker ersetzt jeden SetOCRStatus-Call
durch SetOCRResult und uebergibt die extrahierte Zeichenzahl bei 'done'.

internal/storage/ocr.go

@@ -40,6 +40,57 @@ func (s *Store) SetOCRStatus(ctx context.Context, id, status string) error {
 	return nil
 }
 
+// SetOCRResult atomically writes both ocr_status and ocr_chars in one UPDATE.
+// Used by the OCR worker after a job completes (PROJ-44).
+// chars must be >= 0; for status='failed'/'skipped'/'disabled' callers pass 0.
+// Silently no-ops when no DB is configured.
+func (s *Store) SetOCRResult(ctx context.Context, id, status string, chars int64) error {
+	if s.db == nil {
+		return nil
+	}
+	if id == "" {
+		return errors.New("storage: SetOCRResult: empty id")
+	}
+	switch status {
+	case "pending", "done", "failed", "skipped", "disabled":
+	default:
+		return fmt.Errorf("storage: SetOCRResult: invalid status %q", status)
+	}
+	if chars < 0 {
+		chars = 0
+	}
+	_, err := s.db.Exec(ctx,
+		`UPDATE emails SET ocr_status = $1, ocr_chars = $2 WHERE id = $3`,
+		status, chars, id,
+	)
+	if err != nil {
+		return fmt.Errorf("storage: set ocr result: %w", err)
+	}
+	return nil
+}
+
+// GetOCRMeta returns ocr_status (defaulting to "pending" if NULL) and
+// ocr_chars (defaulting to 0) for a single mail. Returns "", 0, nil when no
+// DB is configured or the mail is not found.
+func (s *Store) GetOCRMeta(ctx context.Context, id string) (status string, chars int64, err error) {
+	if s.db == nil {
+		return "", 0, nil
+	}
+	if id == "" {
+		return "", 0, errors.New("storage: GetOCRMeta: empty id")
+	}
+	row := s.db.QueryRow(ctx,
+		`SELECT COALESCE(ocr_status, 'pending'), COALESCE(ocr_chars, 0)
+		   FROM emails WHERE id = $1`, id)
+	if scanErr := row.Scan(&status, &chars); scanErr != nil {
+		if errors.Is(scanErr, pgx.ErrNoRows) {
+			return "", 0, nil
+		}
+		return "", 0, fmt.Errorf("storage: get ocr meta: %w", scanErr)
+	}
+	return status, chars, nil
+}
+
 // OCREnabled reports whether OCR processing should run for the given tenant.
 // Defaults to true when:
 //   - no DB is configured (DB-less mode)