Remove RECON daily post

[redreceipt]

Summary

• remove the RECON daily Slack post and its scheduler/debug hooks
• delete the Linear helpers that were only used by that RECON workflow
• update the scheduler/debug tests to match the smaller job surface

Testing

• python3.12 -m unittest tests.test_jobs
• python3.12 -m py_compile jobs.py linear/issues.py linear/projects.py tests/test_jobs.py tests/test_linear_projects.py

Notes

• python3.12 -m unittest tests.test_linear_projects is not runnable in this environment because the gql dependency is not installed locally