refactor: use shared.ToLittleEndian in graphics commands

[adcondev]

This PR refactors StoreRasterGraphicsInBuffer and StoreColumnGraphicsInBuffer in pkg/commands/bitimage/graphics_commands.go to use shared.ToLittleEndian instead of manual bitwise operations for converting totalSize to little-endian bytes.

Changes:

• Replaced manual endian conversion for pL and pH with shared.ToLittleEndian(uint16(totalSize)).
• Applied the change to both raster and column graphics commands.

Verification:

• Verified that totalSize is checked against MaxStandardCommandSize (65535) before conversion, ensuring it fits in uint16.
• Ran existing tests go test -v ./pkg/commands/bitimage/... which passed.
• Verified that go vet passes.

---

PR created automatically by Jules for task 3541477053345523575 started by @adcondev

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[github-actions]

👋 Thanks for opening this PR, @adcondev!

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[github-actions]

⚡ Benchmark Results

📈 Performance Comparison

📊 Click to expand detailed results

Current Branch Results

BenchmarkNewDocument-4    	1000000000	         0.2889 ns/op	       0 B/op	       0 allocs/op
BenchmarkBuildSimple-4    	 3506148	       334.1 ns/op	     240 B/op	       4 allocs/op
BenchmarkBuildComplex-4   	  425260	      2785 ns/op	    1809 B/op	      25 allocs/op
BenchmarkToJSON-4         	  613647	      2000 ns/op	     592 B/op	       3 allocs/op
BenchmarkParseDocument_Minimal-4    	  529725	      2219 ns/op	     568 B/op	      14 allocs/op
BenchmarkParseDocument_Receipt-4    	  107721	     10910 ns/op	    2392 B/op	      34 allocs/op
BenchmarkCommandUnmarshal_Text-4    	  444865	      2616 ns/op	     568 B/op	      19 allocs/op
BenchmarkCommandUnmarshal_Table-4   	  288750	      4026 ns/op	     944 B/op	      21 allocs/op
BenchmarkTextCommandParsing-4       	  556839	      2069 ns/op	     544 B/op	      16 allocs/op
BenchmarkTableCommandParsing-4      	  265264	      4461 ns/op	    1000 B/op	      29 allocs/op
BenchmarkParseHexString-4           	 8653726	       138.6 ns/op	      48 B/op	       2 allocs/op
BenchmarkCleanHexString-4           	 7153789	       172.7 ns/op	      64 B/op	       2 allocs/op
BenchmarkContainsSequence-4         	312380020	         3.891 ns/op	       0 B/op	       0 allocs/op
BenchmarkCheckCriticalCommands-4    	29056934	        40.95 ns/op	       0 B/op	       0 allocs/op
BenchmarkDocument_Validate-4       	16496112	        72.08 ns/op	       0 B/op	       0 allocs/op
BenchmarkParseDocument_Simple-4    	  504891	      2216 ns/op	     568 B/op	      14 allocs/op
BenchmarkParseDocument_Complex-4   	  160520	      7341 ns/op	    1352 B/op	      26 allocs/op
BenchmarkPrintImage_Small-4             	     444	   2577932 ns/op	 3469931 B/op	      24 allocs/op
BenchmarkPrintImage_Medium-4            	     260	   4712673 ns/op	 5481077 B/op	      24 allocs/op
BenchmarkPrintImage_ThermalPreview-4    	     139	   9156085 ns/op	 5235265 B/op	  230723 allocs/op

Base Branch Results

BenchmarkNewDocument-4    	1000000000	         0.2895 ns/op	       0 B/op	       0 allocs/op
BenchmarkBuildSimple-4    	 3466322	       341.9 ns/op	     240 B/op	       4 allocs/op
BenchmarkBuildComplex-4   	  421416	      2749 ns/op	    1809 B/op	      25 allocs/op
BenchmarkToJSON-4         	  599252	      1939 ns/op	     592 B/op	       3 allocs/op
BenchmarkParseDocument_Minimal-4    	  543781	      2149 ns/op	     568 B/op	      14 allocs/op
BenchmarkParseDocument_Receipt-4    	  110534	     10809 ns/op	    2392 B/op	      34 allocs/op
BenchmarkCommandUnmarshal_Text-4    	  450585	      2665 ns/op	     568 B/op	      19 allocs/op
BenchmarkCommandUnmarshal_Table-4   	  296224	      3984 ns/op	     944 B/op	      21 allocs/op
BenchmarkTextCommandParsing-4       	  562518	      2039 ns/op	     544 B/op	      16 allocs/op
BenchmarkTableCommandParsing-4      	  250311	      4449 ns/op	    1000 B/op	      29 allocs/op
BenchmarkParseHexString-4           	 8608809	       139.6 ns/op	      48 B/op	       2 allocs/op
BenchmarkCleanHexString-4           	 7258054	       165.1 ns/op	      64 B/op	       2 allocs/op
BenchmarkContainsSequence-4         	322122595	         3.850 ns/op	       0 B/op	       0 allocs/op
BenchmarkCheckCriticalCommands-4    	29103387	        40.89 ns/op	       0 B/op	       0 allocs/op
BenchmarkDocument_Validate-4       	16525442	        72.27 ns/op	       0 B/op	       0 allocs/op
BenchmarkParseDocument_Simple-4    	  546948	      2142 ns/op	     568 B/op	      14 allocs/op
BenchmarkParseDocument_Complex-4   	  165154	      7164 ns/op	    1352 B/op	      26 allocs/op
BenchmarkPrintImage_Small-4             	     561	   2036954 ns/op	 3469930 B/op	      24 allocs/op
BenchmarkPrintImage_Medium-4            	     297	   4112312 ns/op	 5481074 B/op	      24 allocs/op
BenchmarkPrintImage_ThermalPreview-4    	     151	   7933409 ns/op	 5235275 B/op	  230723 allocs/op

💡 Note: Use benchstat for statistical comparison

🎯 Summary

• Total Benchmarks: 32
• Average Speed: 3073750 ns/op
• Average Memory: 2381091 B/op
• Average Allocations: 41093 allocs/op