Add -out option for file output and fix stdin detection logic

- Add -out/-o option to save decode/encode output to files
- Encoded files are saved as binary, console still shows hex strings
- Decoded XML files are saved as text
- Fix stdin detection logic to prioritize command line arguments
- Add missing System.Collections.Generic import for List<string> usage
- File extension auto-processing now supports -out option
- Clean up data folder with renamed files (data0-3.dump/xml)

🤖 Generated with [Claude Code](https://claude.ai/code)

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

Data/Dump/03-V2GMSG-SAP_SupportedAppProtocolReq.txt

@@ -0,0 +1,8 @@
+0000   80 34 28 2e 23 dd 10 22 33 44 55 66 86 dd 60 00   .4(.#.."3DUf..`.
+0010   00 00 00 40 06 ff fe 80 00 00 00 00 00 00 12 22   ...@..........."
+0020   33 ff fe 44 55 66 fe 80 00 00 00 00 00 00 82 34   3..DUf.........4
+0030   28 ff fe 2e 23 dd c3 65 d1 21 00 63 9b 07 2c c5   (...#..e.!.c..,.
+0040   4a 30 50 18 11 1c d4 f8 00 00 01 fe 80 01 00 00   J0P.............
+0050   00 24 80 00 eb ab 93 71 d3 4b 9b 79 d1 89 a9 89   .$.....q.K.y....
+0060   89 c1 d1 91 d1 91 81 89 99 d2 6b 9b 3a 23 2b 30   ..........k.:#+0
+0070   02 00 00 0c 38 40                                 ....8@