feat(cron): add Run Continuity toggle + badge (#924) (#932)

Expose backend cron self-continuity (context_from=["self"]) in the Cron
editor. Adds a Run Continuity checkbox to the job editor that sends
context_from=["self"] on create and update (null when off, clearing it),
prefills from the loaded job's context_from, and shows a "Continuity" badge
on recurring jobs in the list. context_from was already on CronJob and
CreateCronJobRequest, so this is editor/list wiring only. Strings added for
en/zh/ko. Includes two ViewModel tests.

Co-authored-by: M57 <hy4ri@users.noreply.github.com>

app/src/main/res/values-zh/strings.xml

@@ -729,6 +729,9 @@
     <string name="cron_edit_field_script">脚本</string>
     <string name="cron_edit_field_workdir">工作目录</string>
     <string name="cron_edit_field_no_agent">无 Agent（仅脚本）</string>
+    <string name="cron_edit_field_run_continuity">运行连续性</string>
+    <string name="cron_edit_hint_run_continuity">将本任务上一次的输出注入到每次运行中</string>
+    <string name="cron_badge_continuity">连续</string>
     <string name="cron_edit_monitor_mode">监控模式</string>
     <string name="cron_edit_monitor_off">关</string>
     <string name="cron_edit_monitor_script">脚本</string>