Feature/manual task entry shortcut

[kRyxar87t]

Related Issue

Closes #1207

Summary

This PR adds a manual task entry fallback to the Smart Paste workflow, allowing users to create tasks directly without relying on AI extraction.

Instead of introducing a new backend endpoint or duplicate save logic, the implementation reuses the existing task creation flow so manually created tasks behave the same as AI-generated tasks.

Changes Made

• Added an inline Manual Task Entry section below the Smart Paste panel.
• Added fields for:
  • Subject
  • Task Title
  • Due Date
  • Notes (optional)
• Populated the Subject dropdown dynamically from existing subjects.
• Added client-side validation for required fields.
• Reused the existing store.addTasks() flow to save manual tasks.
• Cleared the form only after successful task creation.
• Kept the existing AI extraction workflow unchanged.

Testing

Tested locally by:

• Creating tasks manually using the new form.
• Verifying required field validation.
• Confirming tasks are saved successfully.
• Confirming newly created tasks appear in the planner and task list.
• Confirming AI extraction continues to work without regression.

Screenshots

Before

After

Checklist

• Code follows project style
• Tested locally
• No unrelated changes included
• Documentation updated (if applicable)