Add custom interval days support for task frequency

Backend changes:
- Add "Custom" frequency option to database seeds
- Add custom_interval_days field to Task model
- Update task DTOs to accept custom_interval_days
- Update task service to use custom_interval_days for next due date calculation

🤖 Generated with [Claude Code](https://claude.com/claude-code)

Co-Authored-By: Claude Opus 4.5 <noreply@anthropic.com>

internal/dto/requests/task.go

@@ -60,6 +60,7 @@ type CreateTaskRequest struct {
 	CategoryID         *uint            `json:"category_id"`
 	PriorityID         *uint            `json:"priority_id"`
 	FrequencyID        *uint            `json:"frequency_id"`
+	CustomIntervalDays *int             `json:"custom_interval_days"` // For "Custom" frequency, user-specified days
 	InProgress         bool             `json:"in_progress"`
 	AssignedToID       *uint            `json:"assigned_to_id"`
 	DueDate            *FlexibleDate    `json:"due_date"`
@@ -74,6 +75,7 @@ type UpdateTaskRequest struct {
 	CategoryID         *uint            `json:"category_id"`
 	PriorityID         *uint            `json:"priority_id"`
 	FrequencyID        *uint            `json:"frequency_id"`
+	CustomIntervalDays *int             `json:"custom_interval_days"` // For "Custom" frequency, user-specified days
 	InProgress         *bool            `json:"in_progress"`
 	AssignedToID       *uint            `json:"assigned_to_id"`
 	DueDate            *FlexibleDate    `json:"due_date"`

internal/models/task.go

@@ -67,6 +67,7 @@ type Task struct {
 	Priority      *TaskPriority    `gorm:"foreignKey:PriorityID" json:"priority,omitempty"`
 	FrequencyID   *uint            `gorm:"column:frequency_id;index" json:"frequency_id"`
 	Frequency     *TaskFrequency   `gorm:"foreignKey:FrequencyID" json:"frequency,omitempty"`
+	CustomIntervalDays *int        `gorm:"column:custom_interval_days" json:"custom_interval_days"` // For "Custom" frequency, user-specified days
 
 	// In Progress flag - replaces status lookup
 	InProgress    bool             `gorm:"column:in_progress;default:false;index" json:"in_progress"`

internal/services/task_service.go

@@ -178,6 +178,7 @@ func (s *TaskService) CreateTask(req *requests.CreateTaskRequest, userID uint) (
 		CategoryID:         req.CategoryID,
 		PriorityID:         req.PriorityID,
 		FrequencyID:        req.FrequencyID,
+		CustomIntervalDays: req.CustomIntervalDays,
 		InProgress:         req.InProgress,
 		AssignedToID:       req.AssignedToID,
 		DueDate:            dueDate,
@@ -237,6 +238,9 @@ func (s *TaskService) UpdateTask(taskID, userID uint, req *requests.UpdateTaskRe
 	if req.FrequencyID != nil {
 		task.FrequencyID = req.FrequencyID
 	}
+	if req.CustomIntervalDays != nil {
+		task.CustomIntervalDays = req.CustomIntervalDays
+	}
 	if req.InProgress != nil {
 		task.InProgress = *req.InProgress
 	}
@@ -534,15 +538,25 @@ func (s *TaskService) CreateCompletion(req *requests.CreateTaskCompletionRequest
 
 	// Update next_due_date and in_progress based on frequency
 	// - If frequency is "Once" (days = nil or 0), set next_due_date to nil (marks as completed)
+	// - If frequency is "Custom", use task.CustomIntervalDays for recurrence
 	// - If frequency is recurring, calculate next_due_date = completion_date + frequency_days
 	//   and reset in_progress to false so task shows in correct kanban column
-	if task.Frequency == nil || task.Frequency.Days == nil || *task.Frequency.Days == 0 {
+	var intervalDays *int
+	if task.Frequency != nil && task.Frequency.Name == "Custom" {
+		// Custom frequency - use task's custom_interval_days
+		intervalDays = task.CustomIntervalDays
+	} else if task.Frequency != nil {
+		// Standard frequency - use frequency's days
+		intervalDays = task.Frequency.Days
+	}
+
+	if intervalDays == nil || *intervalDays == 0 {
 		// One-time task - clear next_due_date (completion is determined by NextDueDate == nil + has completions)
 		task.NextDueDate = nil
 		task.InProgress = false
 	} else {
-		// Recurring task - calculate next due date from completion date + frequency
-		nextDue := completedAt.AddDate(0, 0, *task.Frequency.Days)
+		// Recurring task - calculate next due date from completion date + interval
+		nextDue := completedAt.AddDate(0, 0, *intervalDays)
 		task.NextDueDate = &nextDue
 
 		// Reset in_progress to false so task appears in upcoming/due_soon
@@ -630,7 +644,15 @@ func (s *TaskService) QuickComplete(taskID uint, userID uint) error {
 	}
 
 	// Update next_due_date and in_progress based on frequency
-	if task.Frequency == nil || task.Frequency.Days == nil || *task.Frequency.Days == 0 {
+	// Determine interval days: Custom frequency uses task.CustomIntervalDays, otherwise use frequency.Days
+	var quickIntervalDays *int
+	if task.Frequency != nil && task.Frequency.Name == "Custom" {
+		quickIntervalDays = task.CustomIntervalDays
+	} else if task.Frequency != nil {
+		quickIntervalDays = task.Frequency.Days
+	}
+
+	if quickIntervalDays == nil || *quickIntervalDays == 0 {
 		// One-time task - clear next_due_date (completion is determined by NextDueDate == nil + has completions)
 		log.Info().
 			Uint("task_id", task.ID).
@@ -639,12 +661,16 @@ func (s *TaskService) QuickComplete(taskID uint, userID uint) error {
 		task.NextDueDate = nil
 		task.InProgress = false
 	} else {
-		// Recurring task - calculate next due date from completion date + frequency
-		nextDue := completedAt.AddDate(0, 0, *task.Frequency.Days)
+		// Recurring task - calculate next due date from completion date + interval
+		nextDue := completedAt.AddDate(0, 0, *quickIntervalDays)
+		frequencyName := "unknown"
+		if task.Frequency != nil {
+			frequencyName = task.Frequency.Name
+		}
 		log.Info().
 			Uint("task_id", task.ID).
-			Str("frequency_name", task.Frequency.Name).
-			Int("frequency_days", *task.Frequency.Days).
+			Str("frequency_name", frequencyName).
+			Int("interval_days", *quickIntervalDays).
 			Time("completed_at", completedAt).
 			Time("next_due_date", nextDue).
 			Msg("QuickComplete: Recurring task, setting next_due_date")

seeds/001_lookups.sql

@@ -65,7 +65,8 @@ VALUES
     (5, NOW(), NOW(), 'Monthly', 30, 5),
     (6, NOW(), NOW(), 'Quarterly', 90, 6),
     (7, NOW(), NOW(), 'Semi-Annually', 180, 7),
-    (8, NOW(), NOW(), 'Annually', 365, 8)
+    (8, NOW(), NOW(), 'Annually', 365, 8),
+    (9, NOW(), NOW(), 'Custom', NULL, 9)
 ON CONFLICT (id) DO UPDATE SET
     name = EXCLUDED.name,
     days = EXCLUDED.days,