Support Task Dependency Linking with Predecessor/Successor Relationships #532

✨ Feature Request

Is your feature request related to a problem? Please describe.
Kan.bn currently treats all tasks as independent items. This becomes limiting when working with multi-step workflows where certain tasks must be completed before others can begin. Without dependency tracking, it's easy to accidentally start work on tasks that are actually blocked, or lose track of multi-stage processes.

Describe the solution you'd like
Add support for task dependencies using predecessors and successors.

• A predecessor is a task that must be completed before the current task can start.
• A successor is a task that depends on the current task's completion.

Desired functionality:

• Ability to link tasks together via predecessor/successor relationships.
• Visual indicators showing when a task is blocked.
• Optional enforcement preventing a task from being moved to "In Progress" or "Done" until its predecessors are complete.
• Quick navigation between linked tasks.
• A dependency list or lightweight graph showing upstream and downstream tasks.

Additional context
Task dependencies are a common feature in project management tools. Adding them to Kan.bn would allow more complex workflows without sacrificing the lightweight feel of the app. This is especially useful for engineering pipelines, content creation flows, and multi-step operational processes.

Implementation ideas

• Add a "Dependencies" section in the task modal to select predecessors and successors.
• Store dependency relationships as arrays of task IDs in the task schema.
• Display dependency badges on cards (e.g., "Blocked by # 123").

Screenshots/Mockups

Would you like to work on this feature?

• Yes, I'd like to help implement this feature
• No, I'm just suggesting the feature