Add container-native scheduled task system with timezone support

Introduces a cron-based scheduler that lets Claude set up recurring and
one-time tasks inside containers. Tasks run as separate Claude Code agents
and persist across container recreation via the named volume.

New files:
- container/triple-c-scheduler: CLI for add/remove/enable/disable/list/logs/run/notifications
- container/triple-c-task-runner: cron wrapper with flock, logging, notifications, auto-cleanup

Key changes:
- Dockerfile: add cron package and COPY both scripts
- entrypoint.sh: timezone setup, cron daemon, crontab restore, env saving
- container.rs: init=true for zombie reaping, TZ env, scheduler instructions, timezone recreation check
- image.rs: embed scheduler scripts in build context
- app_settings.rs + types.ts: timezone field
- settings_commands.rs: detect_host_timezone via iana-time-zone crate
- SettingsPanel.tsx: timezone input with auto-detection

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

container/Dockerfile

@@ -19,6 +19,7 @@ RUN apt-get update && apt-get install -y --no-install-recommends \
     unzip \
     pkg-config \
     libssl-dev \
+    cron \
     && rm -rf /var/lib/apt/lists/*
 
 # Remove default ubuntu user to free UID 1000 for host-user remapping
@@ -101,5 +102,9 @@ WORKDIR /workspace
 USER root
 COPY entrypoint.sh /usr/local/bin/entrypoint.sh
 RUN chmod +x /usr/local/bin/entrypoint.sh
+COPY triple-c-scheduler /usr/local/bin/triple-c-scheduler
+RUN chmod +x /usr/local/bin/triple-c-scheduler
+COPY triple-c-task-runner /usr/local/bin/triple-c-task-runner
+RUN chmod +x /usr/local/bin/triple-c-task-runner
 
 ENTRYPOINT ["/usr/local/bin/entrypoint.sh"]