fix: catch ErrNeedsFullRecalculation in task creation position conflict resolution

resolvePositionConflictsAfterInsert now falls back to a full position
recalculation when resolveTaskPositionConflicts returns
ErrNeedsFullRecalculation, instead of bubbling the error up as HTTP 500.
This mirrors the existing fallback logic in the CLI repair command.

Ref: #2550

pkg/models/task_position.go

@@ -600,12 +600,20 @@ func resolveTaskPositionConflicts(s *xorm.Session, projectViewID int64, conflict
 // resolvePositionConflictsAfterInsert checks a batch of newly inserted task positions
 // for conflicts (duplicate position values within the same view) and resolves them.
 // This is called after bulk-inserting positions during task creation.
+// If resolveTaskPositionConflicts returns ErrNeedsFullRecalculation for a view,
+// it falls back to a full recalculation of all positions in that view.
 func resolvePositionConflictsAfterInsert(s *xorm.Session, positions []*TaskPosition) error {
 	// Track which (viewID, position) pairs we've already checked to avoid
 	// resolving the same conflict group twice.
 	checked := make(map[int64]map[float64]bool)
+	// Track views that have already been fully recalculated so we skip
+	// further conflict checks for them.
+	recalculated := make(map[int64]bool)
 
 	for _, pos := range positions {
+		if recalculated[pos.ProjectViewID] {
+			continue
+		}
 		if checked[pos.ProjectViewID] != nil && checked[pos.ProjectViewID][pos.Position] {
 			continue
 		}
@@ -624,6 +632,15 @@ func resolvePositionConflictsAfterInsert(s *xorm.Session, positions []*TaskPosit
 		}
 
 		err = resolveTaskPositionConflicts(s, pos.ProjectViewID, conflicts)
+		if IsErrNeedsFullRecalculation(err) {
+			view := &ProjectView{ID: pos.ProjectViewID}
+			err = recalculateTaskPositionsForRepair(s, view)
+			if err != nil {
+				return err
+			}
+			recalculated[pos.ProjectViewID] = true
+			continue
+		}
 		if err != nil {
 			return err
 		}

pkg/models/task_position_test.go

@@ -547,3 +547,49 @@ func TestSetTaskInBucketInViewsResolvesConflicts(t *testing.T) {
 	assert.NotEqual(t, p1.Position, p2.Position,
 		"Positions should be unique after conflict resolution")
 }
+
+func TestResolvePositionConflictsAfterInsertFallsBackToRecalculation(t *testing.T) {
+	db.LoadAndAssertFixtures(t)
+	s := db.NewSession()
+	defer s.Close()
+
+	viewID := int64(1)
+
+	// Clear existing positions for this view
+	_, err := s.Where("project_view_id = ?", viewID).Delete(&TaskPosition{})
+	require.NoError(t, err)
+
+	// Set up extremely tight spacing that forces ErrNeedsFullRecalculation:
+	// Two existing positions with a gap smaller than MinPositionSpacing * (conflicts+1)
+	basePos := 100.0
+	tinyGap := MinPositionSpacing * 0.1 // Much smaller than needed
+	_, err = s.Insert(&TaskPosition{TaskID: 800, ProjectViewID: viewID, Position: basePos})
+	require.NoError(t, err)
+	_, err = s.Insert(&TaskPosition{TaskID: 801, ProjectViewID: viewID, Position: basePos + tinyGap})
+	require.NoError(t, err)
+	_, err = s.Insert(&TaskPosition{TaskID: 802, ProjectViewID: viewID, Position: basePos + tinyGap})
+	require.NoError(t, err)
+	_, err = s.Insert(&TaskPosition{TaskID: 803, ProjectViewID: viewID, Position: basePos + 2*tinyGap})
+	require.NoError(t, err)
+
+	// The conflicting positions that would trigger ErrNeedsFullRecalculation
+	conflictPositions := []*TaskPosition{
+		{TaskID: 801, ProjectViewID: viewID, Position: basePos + tinyGap},
+		{TaskID: 802, ProjectViewID: viewID, Position: basePos + tinyGap},
+	}
+
+	// This should NOT return an error -- it should fall back to full recalculation
+	err = resolvePositionConflictsAfterInsert(s, conflictPositions)
+	require.NoError(t, err)
+
+	// Verify all positions are now unique
+	var positions []*TaskPosition
+	err = s.Where("project_view_id = ?", viewID).OrderBy("position ASC").Find(&positions)
+	require.NoError(t, err)
+
+	seen := make(map[float64]bool)
+	for _, p := range positions {
+		assert.False(t, seen[p.Position], "duplicate position found: %f for task %d", p.Position, p.TaskID)
+		seen[p.Position] = true
+	}
+}