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/commands/settings_commands.rs

@@ -29,6 +29,33 @@ pub async fn pull_image(
     .await
 }
 
+#[tauri::command]
+pub async fn detect_host_timezone() -> Result<String, String> {
+    // Try the iana-time-zone crate first (cross-platform)
+    match iana_time_zone::get_timezone() {
+        Ok(tz) => return Ok(tz),
+        Err(e) => log::debug!("iana_time_zone::get_timezone() failed: {}", e),
+    }
+
+    // Fallback: check TZ env var
+    if let Ok(tz) = std::env::var("TZ") {
+        if !tz.is_empty() {
+            return Ok(tz);
+        }
+    }
+
+    // Fallback: read /etc/timezone (Linux)
+    if let Ok(tz) = std::fs::read_to_string("/etc/timezone") {
+        let tz = tz.trim().to_string();
+        if !tz.is_empty() {
+            return Ok(tz);
+        }
+    }
+
+    // Default to UTC if detection fails
+    Ok("UTC".to_string())
+}
+
 #[tauri::command]
 pub async fn detect_aws_config() -> Result<Option<String>, String> {
     if let Some(home) = dirs::home_dir() {