fix(ci): reduce Actions usage by windowing News schedules to active UTC hours

[Copilot]

The repo consumed ~3,809 Actions minutes in July. The largest reducible cost was the News and News watchdog workflows, each scheduled hourly (24×/day) but only doing real work during the local active window (odd hours 07:00–21:00 Europe/Amsterdam). Overnight runs booted a runner, gate-skipped in seconds, and were still billed (GitHub rounds each job up to 1 minute).

Changes

• Windowed the two scheduled crons to the UTC hours that can map to the active window across DST, instead of running all 24 hours:
  • News: 7 * * * * → 7 5-20 * * *
  • News watchdog: 37 * * * * → 37 5-20 * * *
• Tests (tests/test_workflows.py): updated schedule assertions.
• Docs (docs/github-actions.md): updated schedule table, cron excerpt, watchdog note, and scheduling rationale.

Why 5-20 UTC

Covers every real-work slot year-round — summer (UTC+2) maps local 07:00 → 05:00 UTC; winter (UTC+1) maps local 21:00 → 20:00 UTC. The overnight UTC hours (21:00–04:00) can never fall in the active window, so scheduling them was pure waste.

Impact

Eliminates ~16 always-skip runs/day (~8 per workflow, ≈480 min/month). No behavior change inside the active window: the in-job cadence gate still selects the exact odd local hours, and the watchdog still self-heals schedule jitter.

Further levers (not included; each trades off a feature)

Lower the briefing cadence (e.g. 3h), run the watchdog every 2h, or drop the redundant full unit-test run in pages.yml's per-deploy test-command.

• Fixes fix(ci): reduce workflow usage #218