Delete temporary planning files

[mairas]

Description

Clean up temporary planning documents now that content is migrated to permanent locations.

Files to Delete

• apt.hatlabs.fi/TASKS.md (this implementation plan)

Acceptance Criteria

• Temporary files deleted
• All content preserved in ARCHITECTURE.md or issues
• Git history clean

Dependencies

• Delete temporary planning files #41 (all documentation updated)

Implementation Requirements

This is a simple cleanup task. Just delete TASKS.md after all implementation is complete.

Related to #28