chore(control-plane): declare aio-fleet ownership

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Summary

• declare this repo's aio-fleet control-plane ownership contract
• remove app-local shared test dependency boilerplate now installed centrally by aio-fleet
• add or update upstream monitor metadata in .aio-fleet.yml where this repo has upstream-tracked versions

What changed

• retired requirements-dev.txt
• kept app-owned runtime/source/template/docs/tests in place
• moved shared dependency and upstream automation expectations to aio-fleet

Why

• aio-fleet now owns shared CI mechanics, dependency installation, upstream monitoring, required checks, release orchestration, registry verification, Trunk, and cleanup verification
• app repos should keep only app-specific implementation and declarative fleet metadata

Validation

• central aio-fleet test suite passed: python -m pytest
• central cleanup verification passed: python -m aio_fleet cleanup-repo --all --verify
• central validation passed: python -m aio_fleet validate --all
• representative central control checks passed after dependency removal for unraid-aio-template, sure-aio, khoj-aio, and signoz-aio
• hosted aio-fleet workflow checks passed for Sure, Dify, SignOz, and upstream monitor dry-run

Notes

• depends on feat(control-plane): add upstream monitor automation aio-fleet#48
• keep this draft until the aio-fleet control-plane PR is merged