feat(web): schedules — auto-create pi sessions on a cadence

[setkyar]

Summary

Adds a Schedules feature: define automations that run pi on a cron/preset cadence (or via Run-now). Each firing creates a fresh pi session, sends the schedule's instructions as the first message, and records the run so created sessions can be filtered and surfaced in a run log. Scheduled runs fire a schedule-specific web push on completion (shown even when the app is foregrounded).

• New /schedules page reached from a calendar button beside the Timeline/Projects toggle on the index.
• Editor with name, instructions, model search, thinking level, project dir (optional → home), and frequency: manual, hourly, daily, weekdays, weekly, or custom cron — all stored as a standard cron expression with a per-schedule IANA timezone.
• Mobile uses a floating + (matching the sessions index); the header "New schedule" button is hidden on small viewports.
• Missed runs while the server was down are skipped on startup.
• Schedules and runs persist in SQLite; run rows double as the session → schedule mapping that tags created sessions and routes the schedule-specific push.

What's in the diff

Backend (Go)

• internal/schedules/ — Schedule/Run types, SQLite store, NextFire via github.com/robfig/cron/v3 (new dep), pure & table-driven tested.
• internal/server/scheduler.go — 30-s tick loop and the fireSchedule runner that creates the session, ensures the worker, and sends instructions.
• internal/server/schedules_api.go — /api/schedules (list/create), /api/schedule (read/update/delete by ?id), /api/schedule/run (Run-now), /api/schedule/runs (log).
• internal/server/push.go — adds NotifyScheduleDone; status.go routes the running→idle transition to a schedule-specific push when the finished session is schedule-created.
• internal/ui/embedded/assets/sw.js — always shows schedule-done notifications (no foreground-suppress, distinct tag).

Frontend (Svelte 5)

• web/src/routes/SchedulesPage.svelte, /schedules route in App.svelte, "Schedules" nav button in IndexHeader.svelte.
• web/src/index/schedules.js — API helpers + cron preset compile/parse (buildCron, parseCron, describeFrequency).
• Polished UI with Lucide icons (Play/Pause/Edit/Runs/Delete), Active/Paused pills, Next/Last meta chips, run log, and a clean editor modal with focus rings.
• All styles live in internal/ui/embedded/styles/schedules.css (the live SPA shell inlines global stylesheets and doesn't link Vite's component CSS — so scoped <style> blocks would render unstyled; this approach matches every other route in the app).
• New schedules.* i18n keys added to all 14 locale files.

Docs & tests

• New docs/sequence-flows/schedules.md + index/backend doc updates.
• Go unit tests (cron, store, run lifecycle, fireSchedule, handlers); Vitest tests for the cron helpers.
• Playwright E2E (e2e/tests/schedules.spec.ts) covers create → Run-now → run log → delete, includes a max-width: 880px styling-applied guard, and is layout-aware (header button on desktop, FAB on mobile). Verified passing on Desktop Chrome, Desktop Safari, and Mobile Chrome.

Test plan

• make check (lint, format, knip, vitest, Go tests, build, vet, install tests) — green locally
• cd e2e && npx playwright test tests/schedules.spec.ts across Desktop Chrome / Safari / Mobile Chrome — 9/9 passed locally
• Manually visit /schedules on desktop and mobile — header button vs floating + behavior, editor open/save, Run-now navigates to created session, run log shows entry, delete removes the card
• Subscribe to push notifications and run a scheduled session to completion — verify the schedule-specific push fires (not the generic "Response ready")