[Bug / UX]: Overlap Detection Does Not Provide Specific Conflict Details to the User

[prince-pokharna]

Summary

DailyForge's conflict detection prevents overlapping tasks on the same day — a core feature highlighted in the README. However, when a conflict is detected, the user receives no actionable information about which existing task is causing the conflict or what time slot is already occupied. This makes the feature feel like a black box and forces users to manually scan the grid to identify the problematic placement.

Problem

• When a task is dropped onto a conflicting time slot, the user sees a generic rejection (the task snaps back), but receives no toast, modal, or inline message identifying the conflict.
• The user does not know: which existing task occupies that slot, what time range is blocked, or which days are available for the dropped task.
• This is particularly problematic for tasks with long durations (e.g., a 3-hour task) where the overlap range is non-obvious from the grid.

Steps to Reproduce

1. Create two tasks with overlapping durations.
2. Drag the second task to the same day/time as the first task.
3. Observe: the task is rejected without any user-facing explanation.

Impact

• New users may assume the drag-and-drop is broken rather than understanding that overlap protection is active.
• The silent rejection is especially confusing on mobile, where the drop zone is smaller and visual feedback is harder to perceive.
• This gap undermines one of the project's core selling points: "Automatically detects and prevents scheduling conflicts."

Proposed Solution

I would like to improve the conflict feedback mechanism as follows:

1. Toast Notification with Conflict Detail: When a drop is rejected, display a toast (using the existing UI pattern in the codebase) with a message such as: "Conflict with '[Task Name]' already scheduled at [Start Time]–[End Time] on [Day]." This requires passing the conflicting task's metadata back from the conflict detection function.

2. Visual Highlight of Conflicting Slot: Briefly highlight the existing conflicting task card with a pulsing red border (CSS @keyframes animation) for 2 seconds after the rejected drop, drawing the user's eye to the conflict source.

3. Suggested Free Slots (stretch goal): Display up to 2 available time slots on the same day where the dropped task would fit, making it easier to reschedule without leaving the drag context.

Tech scope: Frontend only. The conflict detection logic in the Routine Builder component will need to be refactored to return the conflicting task object in addition to a boolean flag.

I would be happy to take this on. Could you assign this issue to me?