feat(spa): wire playout delete/reset/erase + scheduling context + templates preview calendar (#210)

Adds the SPA slice for the newly-merged playout endpoints:
- api/playouts: deletePlayout, resetChannelPlayout, erasePlayoutItems,
  erasePlayoutItemsAndHistory, getPlayoutItemSchedulingContext (+ types).
- PlayoutsScreen: enable per-playout Reset (channel playout reset), Delete
  (danger, confirm), and erase-by-kind buttons (Block = items + items&history;
  Classic/Sequential/Scripted = items&history; none for ExternalJson); replaces
  the stale "no per-playout reset endpoint" block. Disable Alternate schedules
  for OnDemand Classic playouts (Blazor parity).
- Per-item scheduling-context dialog (info button when hasSchedulingContext &&
  id != null), rendering the decoded JSON in a scrollable <pre>.
- Playout-templates editor: "Preview calendar" toggle with a Monday-first month
  grid; winning template per day computed client-side via a colocated
  appliesToDate/firstMatchingIndex helper that ports
  AlternateScheduleSelector.GetScheduleForDate / PlayoutTemplateEditViewModel
  .AppliesToDate exactly (inclusive range, year-wrap reverse, start-day rollover,
  end-day clamp, explicit-year override).
- Button gains a title prop (parity with IconButton) for the disabled-button hint.

Tests: api client URL/method assertions, PlayoutsScreen action flows
(delete/reset/erase per kind, OnDemand gating, scheduling-context dialog +
error), calendar-helper unit tests, and a preview-calendar render test.

Co-Authored-By: Claude Fable 5 <noreply@anthropic.com>

web/src/components/forms.tsx

@@ -20,6 +20,7 @@ export interface ButtonProps {
   type?: 'button' | 'submit' | 'reset';
   onClick?: (e: MouseEvent<HTMLButtonElement>) => void;
   style?: CSSProperties;
+  title?: string;
 }
 
 export function Button({
@@ -33,13 +34,15 @@ export function Button({
   fullWidth = false,
   type = 'button',
   onClick,
-  style
+  style,
+  title
 }: ButtonProps) {
   return (
     <button
       type={type}
       disabled={disabled || loading}
       onClick={onClick}
+      title={title}
       className={classNames(
         'ctv-button',
         `ctv-button-${variant}`,