feat: activity-based worklog suggestions (Step 16)

- Suggestion struct with nodeId, nodeTitle, summary, suggestedMin
- GetSuggestions binding: analyzes today's activity events, groups by
  node, skips nodes with existing today's worklog, generates summary
- AcceptSuggestion binding: creates worklog entry from suggestion
- HasTodayEntries helper on worklog.Service
- Suggestions panel in Worklog tab with Apply button
- i18n: worklog.suggestions / worklog.apply (ru + en)

internal/core/worklog/worklog.go

@@ -140,6 +140,16 @@ func (s *Service) Delete(id string) error {
 	return nil
 }
 
+// HasTodayEntries checks if any worklog entries exist for today.
+func (s *Service) HasTodayEntries(nodeID string) (bool, error) {
+	today := time.Now().Format("2006-01-02")
+	var count int
+	err := s.db.QueryRow(
+		`SELECT COUNT(*) FROM worklog_entries WHERE node_id=? AND date=?`,
+		nodeID, today).Scan(&count)
+	return count > 0, err
+}
+
 // SumMinutes returns total minutes for a node.
 func (s *Service) SumMinutes(nodeID string) (int, error) {
 	var total sql.NullInt64