chore: remove obsolete planning documents

Remove QRInfo and Phase 3 planning documents that are no longer needed
as the implementation has been completed.

- Removed PLAN_QRINFO.md
- Removed PHASE_3_IMPLEMENTATION.md
- Removed PLAN_QRINFO_2.md

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Co-Authored-By: Claude <noreply@anthropic.com>

Author: 2 people