Fix printer detection, implement portable deployment with SumatraPDF

- Fixed network printer enumeration (PRINTER_ENUM_LOCAL | PRINTER_ENUM_CONNECTIONS)
- Added printer name truncation to 20 chars with full name mapping
- Implemented silent PDF printing using SumatraPDF with landscape orientation
- Added auto-dismiss for success popup (3 seconds)
- Bundled SumatraPDF inside executable for portable single-file deployment
- Updated build script to embed SumatraPDF
- Added setup_sumatra.ps1 for downloading SumatraPDF portable
- Added DEPLOYMENT.md documentation

DEPLOYMENT.md

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+# Label Printer - Portable Deployment Guide
+
+## Deployment Structure
+
+The app is now **fully self-contained** with SumatraPDF embedded inside:
+
+```
+LabelPrinter/
+├── LabelPrinter.exe          # Main application (includes SumatraPDF inside)
+├── pdf_backup/               # Auto-created: PDF backups
+└── logs/                     # Auto-created: Print logs
+```
+
+**No visible folders!** SumatraPDF is bundled inside LabelPrinter.exe and extracted to a temporary location at runtime.
+
+## Setup Instructions
+
+### 1. Download SumatraPDF (For Building Only)
+
+**This step is only needed when building the app.** SumatraPDF will be embedded inside the executable.
+
+```powershell
+# PowerShell command to download SumatraPDF
+powershell -ExecutionPolicy Bypass -File setup_sumatra.ps1
+```
+
+This downloads SumatraPDF portable (~5 MB) to the `SumatraPDF` folder.
+
+### 2. Build the Application
+
+```powershell
+.\build_windows.ps1
+```
+
+The build script will:
+- Check for SumatraPDF
+- Bundle it inside the executable
+- Create `dist\LabelPrinter.exe` (~80 MB including all dependencies)
+
+### 3. Deploy
+
+**Simply copy `LabelPrinter.exe` to any Windows machine!**
+
+```
+📁 Deployment (any folder)
+└── LabelPrinter.exe  ← Just this one file!
+```
+
+- No installation needed
+- No additional files or folders
+- Double-click to run
+- Works on any Windows 10/11 machine
+
+## Features
+
+- ✅ **Single Executable** - Everything bundled in one .exe file (~80 MB)
+- ✅ **Fully Portable** - No installation needed, no external dependencies
+- ✅ **Silent Printing** - No PDF viewer windows pop up
+- ✅ **Network Printers** - Supports printers from print servers (e.g. `\\server\printer`)
+- ✅ **PDF Backup** - All labels saved to `pdf_backup/` folder
+- ✅ **Print Logging** - CSV logs in `logs/` folder
+- ✅ **SumatraPDF Hidden** - Embedded inside, not visible to users
+
+## Printer Name Display
+
+Network printer names (e.g. `\\filesibiusb05\ZDesigner_ZQ630`) are automatically shortened to 20 characters in the dropdown for better display. The full printer name is used for actual printing.
+
+## Troubleshooting
+
+### Printing Not Working
+
+1. **Check Printer Connection**: Verify printer is online and accessible
+2. **Check PDF Backup**: Labels are always saved to `pdf_backup/` folder even if printing fails
+3. **Check Logs**: View print logs in `logs/` folder for error messages
+4. **Rebuild App**: If you built the app yourself, ensure `setup_sumatra.ps1` was run first to download SumatraPDF before building
+
+### Network Printers Not Showing
+
+- Network printers must be installed/connected on the machine before running the app
+- For print server printers like `\\filesibiusb05\printer`, ensure the share is accessible
+- Run as administrator if printer enumeration fails
+
+## Notes
+
+- First run may be slower (Kivy initialization)
+- PDF backups are auto-deleted after 5 days
+- Log files are auto-deleted after 5 days
+- Supports Python 3.10-3.13 (Python 3.14+ may have issues with Kivy)