fix: allow 6-field cron expressions with seconds

The cron editor rejected sub-minute expressions like `*/30 * * * * *`
because validation required exactly 5 fields. Now accepts both 5-field
(standard) and 6-field (with seconds) cron expressions.

Also fixes schedule type auto-detection to correctly fall back to
'custom' for 6-field expressions instead of misinterpreting field
positions.

Fixes #819

src/lib/components/cron-editor.svelte

@@ -19,7 +19,7 @@
 	// Detect schedule type from cron expression
 	function detectScheduleType(cron: string): 'daily' | 'weekly' | 'custom' {
 		const parts = cron.split(' ');
-		if (parts.length < 5) return 'custom';
+		if (parts.length !== 5) return 'custom';
 
 		const [min, hr, day, month, dow] = parts;
 
@@ -137,23 +137,15 @@
 		onchange(newValue);
 	}
 
-	// Validate cron expression
+	// Validate cron expression (supports 5-field and 6-field with seconds)
 	function isValidCron(cron: string): boolean {
 		const parts = cron.trim().split(/\s+/);
-		if (parts.length !== 5) return false;
-
-		const [min, hr, day, month, dow] = parts;
+		if (parts.length !== 5 && parts.length !== 6) return false;
 
 		// Basic pattern validation (number, *, */n, range, list)
 		const cronFieldPattern = /^(\*|(\*\/\d+)|\d+(-\d+)?(,\d+(-\d+)?)*)$/;
 
-		return (
-			cronFieldPattern.test(min) &&
-			cronFieldPattern.test(hr) &&
-			cronFieldPattern.test(day) &&
-			cronFieldPattern.test(month) &&
-			cronFieldPattern.test(dow)
-		);
+		return parts.every((part) => cronFieldPattern.test(part));
 	}
 
 	// Human-readable description using cronstrue

src/routes/api/auto-update/[containerName]/+server.ts

@@ -66,7 +66,7 @@ export const POST: RequestHandler = async ({ params, url, request, cookies }) =>
 		let scheduleType: 'daily' | 'weekly' | 'custom' = 'custom';
 		if (cronExpression) {
 			const parts = cronExpression.split(' ');
-			if (parts.length >= 5) {
+			if (parts.length === 5) {
 				const [, , day, month, dow] = parts;
 				if (dow !== '*' && day === '*' && month === '*') {
 					scheduleType = 'weekly';