fix(scheduled-tasks): prevent dual-server double dispatch of daily tasks (#2713)

* fix(scheduled-tasks): claim schedule occurrences across server instances

Two OpenChamber servers sharing project config each armed timers and both
dispatched the same daily/weekly/cron/once slot (#2710). Claim the occurrence
in shared config under a cross-process write lock before creating a session.

Co-authored-by: Serhii Dziupin <makeittech@users.noreply.github.com>

* fix(scheduled-tasks): harden occurrence claim failure and lock ownership

Address PR review blockers: release running-slot bookkeeping when claim
throws, avoid silently dropping an armed occurrence after a due-slack sync,
verify lock-file ownership on release, and cover real on-disk lock behavior.

Co-authored-by: Serhii Dziupin <makeittech@users.noreply.github.com>

* fix(scheduled-tasks): always release running slot on state-write failures

Wrap runTask bookkeeping in finally so claim, manual-start, and completion
lock timeouts cannot stuck-run a task; drop the diskNext claim guard that
suppressed later occurrences; recover unparseable locks via mtime age.

Co-authored-by: Serhii Dziupin <makeittech@users.noreply.github.com>

* fix(scheduled-tasks): stop re-arming past nextRunAt and clear stuck running

Only schedule future nextRunAt values so once-task losers and claim-failed
paths cannot spin delay-0 retries. Clear past once nextRunAt on claim, and on
completion-write failure retry terminal status so manual runNow still returns
the session instead of a hard 500 with lastStatus stuck running.

Co-authored-by: Serhii Dziupin <makeittech@users.noreply.github.com>

* fix(scheduled-tasks): release write chain on lock acquire timeout

withProjectWriteLock left the in-process promise chain pending when
acquireProjectFileLock timed out, wedging every later project write and
stranding runTask before finally. Always release the chain; surface
persistError on run; record once claim failures in task state.

Co-authored-by: Serhii Dziupin <makeittech@users.noreply.github.com>

---------

Co-authored-by: Serhii Dziupin <makeittech@users.noreply.github.com>

packages/ui/src/lib/scheduledTasksApi.ts

@@ -143,7 +143,10 @@ export const syncScheduledTaskLoops = async (projectID: string): Promise<void> =
   await fetchScheduledTasks(projectID);
 };
 
-export const runScheduledTaskNow = async (projectID: string, taskID: string): Promise<{ sessionId?: string }> => {
+export const runScheduledTaskNow = async (
+  projectID: string,
+  taskID: string,
+): Promise<{ sessionId?: string; persistError?: string }> => {
   const safeProjectID = ensureProjectID(projectID);
   const safeTaskID = ensureProjectID(taskID);
   const response = await runtimeFetch(`/api/projects/${encodeURIComponent(safeProjectID)}/scheduled-tasks/${encodeURIComponent(safeTaskID)}/run`, {
@@ -158,5 +161,8 @@ export const runScheduledTaskNow = async (projectID: string, taskID: string): Pr
   const parsed = await response.json().catch(() => null);
   return {
     sessionId: typeof parsed?.sessionId === 'string' && parsed.sessionId.length > 0 ? parsed.sessionId : undefined,
+    persistError: typeof parsed?.persistError === 'string' && parsed.persistError.trim().length > 0
+      ? parsed.persistError.trim()
+      : undefined,
   };
 };