Expanded scheduled tasks + keyboard shortcuts

- scripts/run-task.sh: dispatcher for say / backup / snapshot-prune with
  safe arg handling (message stripped of CR/LF, integer-clamped keep
  count). Logs to ~/logs/mc-dashboard/tasks.log (falls back to /tmp).
- New /api/schedule/tasks GET/POST/DELETE route: stores tasks as
  crontab lines with `# mc-task:<base64(json)>` marker so the UI can
  round-trip them. Strict server-side validation:
    - Cron expression regex (5 fields, * / N / N-N / N,N / */N)
    - say message: 1–120 chars, no newlines/backticks/shell quotes
    - snapshot-prune keep: integer 1–50
    - task id: 16-hex only
  Single-quote-escaped message in the generated shell command.
- ScheduledTasks UI under ServerControls (alongside the existing single
  ScheduledRestart): pick type (Announce / Backup / Prune snapshots),
  preset schedule (daily at HH:MM or every N hours), adds with one
  click. Tasks list shows human-readable schedule + "next in Xh" hint
  computed client-side. Hover-reveal Remove action.
- Admin keyboard shortcuts: when not typing,
    r — refetch the active tab's query keys (toast feedback)
    / — focus the first input/contenteditable in the active panel
    ? — toast the shortcuts cheat sheet
  Chord-free, mirrors existing ⌘K palette and Esc handlers.

Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>

components/ServerControls.tsx

@@ -7,6 +7,7 @@ import { Button } from "@/components/ui/button";
 import { Alert, AlertDescription } from "@/components/ui/alert";
 import { Separator } from "@/components/ui/separator";
 import { Skeleton } from "@/components/ui/skeleton";
+import { ScheduledTasks } from "@/components/ScheduledTasks";
 import { StatusBadge, statusFromServer } from "@/components/StatusBadge";
 import {
   Card,
@@ -191,6 +192,11 @@ export function ServerControls() {
 
         {/* Scheduled restart */}
         <ScheduledRestart />
+
+        <Separator />
+
+        {/* Additional scheduled tasks */}
+        <ScheduledTasks />
       </CardContent>
     </Card>
   );