Cookbook scheduler: calendar events drive model serve windows (experimental, feature-flagged)

Add a calendar-driven scheduler so a user can pick a model in Cookbook, click "Schedule…" instead of "Launch", choose time windows + days of the week + (optional) end date, and have Odysseus auto-launch the serve when the window starts and hard-kill it when the window ends. The calendar IS the source of truth — events on a designated calendar are interpreted as serve schedules, so editing the event in the calendar UI immediately changes the schedule.

Whole feature is gated by setting `cookbook_scheduler_enabled` (default False). Disabling the setting silences the reconciler and the API refuses requests; setting + three new files = entire surface, easy to revert.

New files:
  - src/cookbook_scheduler.py — background reconciler: ticks every 60s, reads next ±90s of calendar events on the designated calendar, launches/kills serves to match. Honors "refuse if GPUs busy" (skips with reason, no retry). Adopts pre-existing manual serves matching the event's model so window-end cleanup still applies. Tags scheduler-owned tasks with `_scheduledBy: <event_uid>` so it never kills serves it doesn't own.
  - routes/cookbook_schedule_routes.py — POST /api/cookbook/schedule/from-cookbook builds RRULE+ICS events from the modal's input (model, slots[], days[], until). GET /upcoming returns the next 24h with per-event status (scheduled / running / adopted / skipped / failed / ended) for the UI. POST /reconcile-now manually kicks the reconciler.
  - static/js/cookbookSchedule.js — Schedule button click handler + modal. Daily/hourly time slot picker, multi-slot ("+ add another time slot"), weekday chips with Weekdays/Weekend/Every-day quicksets, optional Until date. Calls /from-cookbook on save. Whole module is a single IIFE; deleting the file plus its <script> tag removes the UI surface.

Existing files touched (minimal):
  - app.py: register the new router + add the reconcile loop as a startup task (~10 lines, all in one block). Reconcile loop checks the feature flag on every tick, so leaving it running with the flag off costs ~one settings lookup per minute.
  - static/index.html: one new <script> tag for cookbookSchedule.js.
  - static/js/cookbookServe.js: add a "Schedule…" button next to the existing Launch button. Hidden by default; cookbookSchedule.js reveals it after confirming the feature flag is on.
  - static/style.css: ~80 lines for the modal styles (mobile-aware via @media).

User choices baked in:
  - Calendar events are the source of truth.
  - Refuse to launch if GPUs busy (skip + log reason in scheduler.events[uid].reason).
  - Hard kill at event end.
  - No retry on a skipped event within the window.
  - Multi-slot per day supported (one calendar event per slot, shared RRULE).
  - Pre-existing manual serves get adopted at window start so they're killed at end.

Known follow-ups (not in this commit):
  - Settings UI to pick the schedule calendar + toggle the feature flag.
  - Calendar event color/badge for status (running/skipped/failed).
  - "Lazy launch on first request" — currently launches at event start. Replacing _launch_serve with a proxy that defers vllm until the first chat request is a contained future change.

static/js/cookbookServe.js

@@ -744,6 +744,11 @@ function _rerenderCachedModels() {
       // pushes Cancel + Launch to the right.
       panelHtml += `<span class="hwfit-serve-actions-spacer"></span>`;
       panelHtml += `<button class="cookbook-btn hwfit-serve-cancel" type="button" title="Close this configuration panel">Cancel</button>`;
+      // Schedule button — opens a modal that converts the current serve
+      // config into a calendar event. Hidden unless the scheduler feature
+      // flag is on (cookbookSchedule.js reads /api/cookbook/schedule/upcoming
+      // on init and toggles visibility).
+      panelHtml += `<button class="cookbook-btn hwfit-serve-schedule" type="button" title="Schedule this model to run on a recurring window" style="display:none;"><svg width="11" height="11" viewBox="0 0 24 24" fill="none" stroke="currentColor" stroke-width="2" stroke-linecap="round" stroke-linejoin="round" style="vertical-align:-1px;margin-right:4px;flex-shrink:0;"><rect x="3" y="4" width="18" height="18" rx="2" ry="2"/><line x1="16" y1="2" x2="16" y2="6"/><line x1="8" y1="2" x2="8" y2="6"/><line x1="3" y1="10" x2="21" y2="10"/></svg>Schedule…</button>`;
       panelHtml += `<button class="cookbook-btn hwfit-serve-launch"><svg width="11" height="11" viewBox="0 0 24 24" fill="none" stroke="currentColor" stroke-width="2" stroke-linecap="round" stroke-linejoin="round" style="vertical-align:-1px;margin-right:4px;flex-shrink:0;"><polygon points="13 2 3 14 12 14 11 22 21 10 12 10 13 2"/></svg>Launch</button>`;
       panelHtml += `</div>`;
       panelHtml += `</div>`;