feat(tasks): add recurring task support with configurable intervals

[desireddymohithreddy0925]

Summary

Implements a comprehensive recurring tasks engine, allowing users to define daily, weekly, monthly, and custom intervals for tasks, drastically reducing manual data entry for repetitive work.

Closes #2888

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 functionality)
• 📝 Documentation update
• 🎨 Code style update (formatting, renaming)
• ♻️ Refactoring (no functional changes)
• 🧪 Testing
• 🏗️ Build / CI/CD / Infrastructure

Description

This PR fundamentally enhances the task management system by supporting programmatic task cloning based on user-defined recurrence rules.

Changes made:

• Database Schema Upgrades: Introduced a recurrence_config JSONB column to the tasks table via migration, cleanly encompassing the { type, intervalDays, endsAfter } schema. Added a recurrence_count integer to track progression toward the optional endsAfter limits.
• Backend Auto-Generation: Intercepted task completion logic in PUT /api/tasks/[id].
  • Upon successful task completion, the server checks the recurrence config.
  • Dynamically calculates the due_date offset for the next occurrence.
  • Automatically spawns a new task record mimicking the previous one.
  • Safely zeroes out the recurrence_config on the historic task so it doesn't repeatedly trigger.
• Frontend Configuration UI: Rewrote the inline task creation UI in ProjectMilestones.tsx. Users can select recurrence drop-downs and custom intervals before creating the task.
• Visual Cues: Added a subtle Repeat icon next to active recurring tasks to signal their state in the list view.

Testing

• Verified daily, weekly, monthly, and custom date offset calculations mathematically.
• Ensured endsAfter logic correctly terminates the generation cycle.
• Verified that dropping recurrence_config on completed tasks prevents infinite loops.
• Executed local static analysis (pnpm typecheck) seamlessly.

Screenshots / Screen Recording

(Attach a screenshot of the new recurring settings dropdown and the repeat icon indicator next to a task)

[github-actions]

GSSoC Label Checklist 🏷️

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

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