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/web/server/lib/scheduled-tasks/service.js

@@ -152,7 +152,13 @@ export const createScheduledTaskService = (dependencies) => {
     if (!result.ok) {
       throw new OpenChamberControlError(result.error || 'Task run failed', 500, { task: result.task });
     }
-    return { task: result.task, sessionId: result.sessionID };
+    return {
+      task: result.task,
+      sessionId: result.sessionID,
+      ...(typeof result.persistError === 'string' && result.persistError.trim()
+        ? { persistError: result.persistError.trim() }
+        : {}),
+    };
   };
 
   const setEnabled = async (projectID, taskID, enabled) => {