Rename automation repos to effect-named prefixes: `reports-activity` → `reporter-activity`, `workflow-backups` → `task-backups`

[mmcky]

The draft repository-naming standard (QEP-3, discussion at QuantEcon/qeps#7) registers two effect-named automation prefixes: reporter-* for read-only automation that observes and writes reports or digests, and task-* for automation with write access to org resources executing recurring chores. The two incumbents rename into that pair:

Current	New	Why
reports-activity	reporter-activity	Read-only observer writing periodic activity digests
workflow-backups	task-backups	Write-access automation executing a recurring backup chore

workflow- names the mechanism rather than the role (every repository has .github/workflows/), and reports-* would be a single-member family — reasoning recorded in the QEP's alternatives.

Both repos are actively maintained, so per the draft's migration policy the renames ride on normal maintenance rather than a campaign. GitHub auto-redirects the old repo URLs and git remotes.

Checklist per repo:

• Rename the repo in Settings
• Check scheduled workflows, tokens/secrets scopes, and any hard-coded repo paths in workflow files
• Update inbound references (org docs, team manual, dashboards that link the repo)
• Notify anyone with local clones to update remotes