docs: Update CLAUDE.md with Issue #3 completion

- Mark Issue #3 (QR Code Sizing Fixes) as complete
- Add Issue #4 (Layout Max-Width) as next up
- Document implementation details for Issue #3

Co-Authored-By: Claude Opus 4.5 <noreply@anthropic.com>

CLAUDE.md

@@ -128,8 +128,8 @@ This is a fork with UX improvements. Issues are tracked on the Gitea instance ab
 |---|-------|--------|
 | 1 | Inline Creation Modals | ✅ DONE |
 | 2 | Smart Density Defaults | ✅ DONE |
-| 3 | QR Code Sizing Fixes | 🔄 NEXT |
-| 4 | Layout Max-Width | Open |
+| 3 | QR Code Sizing Fixes | ✅ DONE |
+| 4 | Layout Max-Width | 🔄 NEXT |
 | 5 | Temperature Ranges | Open |
 | 6 | Spool Adjustment History | Open |
 | 7 | 3dfilamentprofiles Integration | Open |
@@ -161,11 +161,23 @@ PC: 1.3, WOOD: 1.28, CF: 1.3, PC/ABS: 1.19, HIPS: 1.03
 PVA: 1.23, ASA: 1.05, PP: 0.9, POM: 1.4, PMMA: 1.18, FPE: 2.16
 ```
 
-### Issue #3 Next - QR Code Sizing Fixes
+### Issue #3 Complete - QR Code Sizing Fixes
 
 See upstream issue: https://github.com/Donkie/Spoolman/issues/671
 
+Changes:
+- Removed fixed 50% max-width constraint (now uses fit-content by default)
+- Added `qrCodePadding` setting (0-10mm, default 2mm)
+- Added `qrCodeMaxWidth` setting (0-100%, 0 = auto)
+- Added UI controls with slider + input number for both settings
+
+Files modified:
+- `client/src/pages/printing/printing.tsx` - Added settings to interface
+- `client/src/pages/printing/qrCodePrintingDialog.tsx` - CSS and UI controls
+
+### Issue #4 Next - Layout Max-Width
+
 Plan:
-- Remove fixed 50% width constraint on QR code
-- Add configurable QR padding setting
-- Allow explicit QR code size control
+- Add max-width constraint to main layout for better UX on wide screens
+- Wrap content with centered container (max ~1400px)
+- Add form max-width (~800px) for better readability