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>

app/src-tauri/src/models/app_settings.rs

@@ -68,6 +68,8 @@ pub struct AppSettings {
     pub auto_check_updates: bool,
     #[serde(default)]
     pub dismissed_update_version: Option<String>,
+    #[serde(default)]
+    pub timezone: Option<String>,
 }
 
 impl Default for AppSettings {
@@ -84,6 +86,7 @@ impl Default for AppSettings {
             global_custom_env_vars: Vec::new(),
             auto_check_updates: true,
             dismissed_update_version: None,
+            timezone: None,
         }
     }
 }