fix: one date+time picker, and what a browser walk of the app turned up

[vladenisov]

Summary

These fixes come from walking the app on the demo workspace in a browser, at 1440px and 390px.

• One date+time picker. It replaces the date button and the separate native time field that sat side by side.
  • One button shows both values, e.g. "Oct 8, 2026, 10:00 PM". It opens a calendar with the time field, Now and Done under it.
  • Picking a day moves focus to the time field. Enter or Done closes the picker.
  • The value contract (YYYY-MM-DDTHH:mm, local time) is unchanged, so callers are untouched.
• Planned events form:
  • The two pickers had no visible captions; they now read Starts and Ends.
  • The local-time hint and the "Ends after it starts" alert move under the row, so the fields line up.
• Planned events card hid future windows. It queried only the chart's range, so a sale planned for next month vanished right after Add. The card now lists windows from the range start onward. The chart already skips windows it has no buckets for.
• Annotations page: planned-event and annotation rows were flush against the card border. They now have the same inset as the panel header.
• Anomalies list:
  • Times used a 24-hour clock ("Oct 8, 22:00") while the signal's own page said "10:00 PM". The list now uses the app's 12-hour format.
  • On phones, "Incident · open" squeezed the scope name to a few letters. The status word is hidden below sm, as "within total" already is.
• Dev stack:
  • postgres now runs with init: true. Under load, a killed healthcheck probe's orphan was reaped by the postmaster, which read it as a crashed child and restarted the cluster. This also applies to compose.yaml.
  • The dev worker ran one fork per core (8 × ~250 MB) inside a 1 GB limit and was OOM-killed mid-task. It now runs --concurrency from CELERY_WORKER_CONCURRENCY, default 2.

Test plan

• Vitest: picker, monitoring, annotations and anomalies suites (170 + 72).
• New hook test usePlannedEvents.test.tsx.
• tsc -b and bun run lint pass.
• New e2e date-time-picker.spec.ts passes locally against the dev stack. It drives both pickers, Enter and Done, then reads the stored instants back.
• Screenshots checked at 1440px and 390px after the fixes.
• CI.

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