Fix label fitting on single DK-22210 page

- Reduced padding (1.5mm → 1mm), barcode height (7mm → 6mm)
- Tighter line heights, combined serial/voltage on one line
- Barcode text size 14 → 12 to reduce image height
- Vertical flex layout instead of horizontal (no QR = more space)
- Should now fit within 29mm height without overflow

Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>

src/lib/server/barcode.ts

@@ -8,7 +8,7 @@ export async function generateBarcodeSvg(text: string): Promise<string> {
 		scale: 3,
 		height: 8,
 		includetext: true,
-		textsize: 14,
+		textsize: 12,
 		textxalign: 'center'
 	});