Week view flexibility: configurable day count, layout, and a CalDAV task list

- Day count (2-10, was fixed at 7) -- 5 days trims the weekend clutter
  without losing the grid format.
- Layout choice: days side by side (original behavior) or stacked
  vertically as full agenda-style sections (reuses _draw_agenda_day,
  same approach _build_today_tomorrow already used for a fixed 2 days).
- Optional task list (CalDAV VTODO collections only -- a plain ICS
  subscription doesn't meaningfully have one) that takes the space of
  one day slot instead of adding an extra one. Same owner-controls-
  their-own-data permission split as calendar sources: only the
  calendar's owner can point a frame's task list at it, but anyone
  linked to the frame can clear it.

Browse-offset paging now moves by N days (was hardcoded to weeks),
identical to the old behavior when days=7. Changing the day count
resets the browse offset, same reasoning as changing views already did.

server/app/static/frame_calendar.js

@@ -8,6 +8,8 @@ document.getElementById('calendar-config-form').addEventListener('submit', async
   const body = new URLSearchParams({
     calendar_view: document.getElementById('calendar_view').value,
     calendar_week_start: document.getElementById('calendar_week_start').value,
+    calendar_week_days: document.getElementById('calendar_week_days').value,
+    calendar_week_layout: document.getElementById('calendar_week_layout').value,
     calendar_photo_inlay: String(document.getElementById('calendar_photo_inlay').checked),
   });
   try {
@@ -162,6 +164,61 @@ document.getElementById('weather-city-add').addEventListener('click', async () =
   }
 });
 
+document.getElementById('tasks_enabled').addEventListener('change', async (e) => {
+  const el = e.target;
+  try {
+    const resp = await fetch(`${window.FRAME_API}/config`, {
+      method: 'POST',
+      headers: { 'Content-Type': 'application/x-www-form-urlencoded' },
+      body: new URLSearchParams({ calendar_tasks_enabled: String(el.checked) }),
+    });
+    if (!resp.ok) throw new Error(await apiError(resp));
+    showStatus(true, 'Saved.');
+    loadCalendarPreview();
+  } catch (e) {
+    el.checked = !el.checked;
+    showStatus(false, e.message);
+  }
+});
+
+// Choosing one of your own CalDAV task lists as this frame's source --
+// owner-only (see api_frames.py's api_tasks_source), so these radios
+// only ever render for the viewer's own calendars anyway.
+document.querySelectorAll('.tasks-source-choice').forEach((el) => {
+  el.addEventListener('change', async () => {
+    try {
+      const resp = await fetch(`${window.FRAME_API}/tasks-source`, {
+        method: 'POST',
+        headers: { 'Content-Type': 'application/json' },
+        body: JSON.stringify({ calendar_key: el.dataset.key }),
+      });
+      if (!resp.ok) throw new Error(await apiError(resp));
+      showStatus(true, 'Task list saved. Reload to see the updated source.');
+      loadCalendarPreview();
+    } catch (e) {
+      showStatus(false, e.message);
+    }
+  });
+});
+
+const tasksSourceClear = document.getElementById('tasks-source-clear');
+if (tasksSourceClear) {
+  tasksSourceClear.addEventListener('click', async () => {
+    try {
+      const resp = await fetch(`${window.FRAME_API}/tasks-source`, {
+        method: 'POST',
+        headers: { 'Content-Type': 'application/json' },
+        body: JSON.stringify({ calendar_key: null }),
+      });
+      if (!resp.ok) throw new Error(await apiError(resp));
+      showStatus(true, 'Task list cleared. Reload to see the change.');
+      loadCalendarPreview();
+    } catch (e) {
+      showStatus(false, e.message);
+    }
+  });
+}
+
 function loadCalendarPreview() {
   document.getElementById('calendar-preview').src = `${window.FRAME_API}/preview/calendar?_=${Date.now()}`;
 }