8 blueprints each defined an identical _bad() (two variants: with/without
detail). Extracted error_response() into api/_responses.py; each blueprint
now imports it `as _bad` so call sites are unchanged. The detail-aware
canonical subsumes both variants. Left settings.py's distinct _bad_int and
the inline jsonify error sites (not duplicated helpers).
Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>
D1 scheduler visibility: AppSetting last-tick stamp on every Beat tick +
GET /api/sources/schedule-status (last_tick_at/next_due_at/due_now/auto_sources)
+ SchedulerStatusBar on the Subscriptions tab (re-polled every 30s).
D2 failing-source rollup: ?failing=true on the sources list + FailingSourcesCard
on Downloads with per-source and bulk "retry" (re-runs the feed via /check).
D3 activity sparkline: GET /api/downloads/activity hourly buckets + CSS bar
chart by the stat chips (failures stacked in error color); refreshes on live poll.
D4 credential staleness: surface last_verified age + "re-verify recommended"
warning past 30d; also fixes the dead last_verified_at field-name mismatch so
the verification row renders at all.
Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>
bvandeusen