feat: implement custom workflow stages with drag-and-drop kanban configuration (#3183)

[knoxiboy]

Summary

This PR implements custom workflow stages with a fully functional drag-and-drop Kanban column and task configuration system. It allows teams/users to create project boards, define custom workflow stages (e.g. Design Review, QA, Staging), and reorder columns or move tasks between them using drag-and-drop.

Closes #3183

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Type of Change

• 🐛 Bug fix (non-breaking change that fixes an issue)
• ✨ New feature (non-breaking change that adds functionality)
• 💥 Breaking change (fix or feature that changes existing behavior)
• 📝 Documentation update
• ♻️ Refactor / code cleanup (no functional change)
• ⚡ Performance improvement
• 🔒 Security fix
• 🧪 Tests only

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What Changed

• Database / Schema:
  • supabase/migrations/20260715000000_add_kanban_boards.sql: Created projects, workflow_stages, and tasks tables with appropriate indexes, references, and Row-Level Security (RLS) policies.
• Backend / API routes:
  • src/app/api/kanban/route.ts: Project creation and retrieval.
  • src/app/api/kanban/[projectId]/route.ts: Project retrieval and deletion.
  • src/app/api/kanban/[projectId]/stages/route.ts: Creating and updating/deleting stages.
  • src/app/api/kanban/[projectId]/tasks/route.ts: Creating and updating/deleting tasks.
• Navigation & Translations:
  • src/components/AppNavbar.tsx: Added "Kanban Board" navigation menu item for logged-in sessions.
  • messages/en.json & messages/es.json: Added English and Spanish localizations for the navigation menu.
• Frontend / UI Components:
  • src/app/dashboard/kanban/page.tsx: Landing view lists projects and provides a project creator card.
  • src/app/dashboard/kanban/[projectId]/page.tsx: Kanban workspace wrapper.
  • src/components/kanban/KanbanBoard.tsx: Main board container orchestration using @dnd-kit/core and @dnd-kit/sortable.
  • src/components/kanban/KanbanColumn.tsx: Kanban column representation for stages.
  • src/components/kanban/KanbanTaskCard.tsx: Task card items.
  • src/components/kanban/StageSettingsModal.tsx: Stage manager enabling custom color picking, rename, delete, and reordering.

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How to Test

1. Navigate to /dashboard/kanban (or click "Kanban Board" in the navbar).
2. Create a new project (e.g. "Release 1.0").
3. Verify that the Kanban Board loads with default stages ("To Do", "In Progress", "Done").
4. Click "Add Task" to create a task.
5. Drag and drop the task card to reorder it or move it to a different column.
6. Click "Configure Columns", add a new stage, reorder the stages list using the reorder buttons, choose a color preset, and save. Verify the columns reorder instantly.

Expected result: Projects, columns, and tasks are created and updated seamlessly. Drag-and-drop operations correctly persist task and column ordering to the database.

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Checklist

• Linked the related issue above
• Self-reviewed my own diff
• No unnecessary console.log, debug code, or commented-out blocks
• npm run lint passes locally (Eslint setup failed locally on native dependency issue)
• No TypeScript errors (npm run type-check)
• Added or updated tests where applicable
• Updated documentation / comments if behavior changed

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Accessibility (UI changes only)

• Keyboard navigation works correctly
• Color contrast meets WCAG AA standard
• ARIA labels / roles added where needed
• Tested on mobile / responsive layout

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Additional Context

• Used @dnd-kit/core and @dnd-kit/sortable for fluid, native-feeling drag-and-drop interactions.
• Optimized update queries to use Supabase bulk upserts when reordering stages and tasks.

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[github-actions]

GSSoC Label Checklist 🏷️

@Priyanshu-byte-coder — please apply the appropriate labels before merging:

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