feat: add deadline management frontend (Phase 1G)

- Fristen page with list view (sortable, filterable by status/case)
- Calendar view with month navigation and deadline dots
- Deadline calculator page (proceeding type + trigger date = timeline)
- Traffic light urgency: red (overdue), amber (this week), green (OK)
- Backend: GET /api/deadlines (all tenant deadlines), GET /api/proceeding-types
- API client: added patch() method
- Types: DeadlineRule, ProceedingType, CalculatedDeadline, RuleTreeNode

backend/internal/services/deadline_service.go

@@ -21,6 +21,23 @@ func NewDeadlineService(db *sqlx.DB) *DeadlineService {
 	return &DeadlineService{db: db}
 }
 
+// ListAll returns all deadlines for a tenant, ordered by due_date
+func (s *DeadlineService) ListAll(tenantID uuid.UUID) ([]models.Deadline, error) {
+	query := `SELECT id, tenant_id, case_id, title, description, due_date, original_due_date,
+	                 warning_date, source, rule_id, status, completed_at,
+	                 caldav_uid, caldav_etag, notes, created_at, updated_at
+	          FROM deadlines
+	          WHERE tenant_id = $1
+	          ORDER BY due_date ASC`
+
+	var deadlines []models.Deadline
+	err := s.db.Select(&deadlines, query, tenantID)
+	if err != nil {
+		return nil, fmt.Errorf("listing all deadlines: %w", err)
+	}
+	return deadlines, nil
+}
+
 // ListForCase returns all deadlines for a case, scoped to tenant
 func (s *DeadlineService) ListForCase(tenantID, caseID uuid.UUID) ([]models.Deadline, error) {
 	query := `SELECT id, tenant_id, case_id, title, description, due_date, original_due_date,