🔒 Fix DoS vulnerability in JSON file loading

[adcondev]

This PR addresses a potential Denial of Service (DoS) vulnerability in the CLI's JSON loading mechanism.
Previously, os.ReadFile would load the entire file into memory without checking its size.
This fix implements a strict size limit of 10MB using io.LimitReader and os.Stat checks.

Changes:

• Added MaxJSONSize (10MB) to pkg/constants.
• Refactored loadJSON in cmd/poster/parsing.go to securely read files.
• Added cmd/poster/parsing_test.go to verify the fix with large and boundary-case files.

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PR created automatically by Jules for task 42113601145997800 started by @adcondev

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[github-actions]

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[github-actions]

⚡ Benchmark Results

📈 Performance Comparison

📊 Click to expand detailed results

Current Branch Results

BenchmarkNewDocument-4    	1000000000	         0.3127 ns/op	       0 B/op	       0 allocs/op
BenchmarkBuildSimple-4    	 3660445	       333.1 ns/op	     240 B/op	       4 allocs/op
BenchmarkBuildComplex-4   	  396436	      2992 ns/op	    1809 B/op	      25 allocs/op
BenchmarkToJSON-4         	  513376	      2151 ns/op	     592 B/op	       3 allocs/op
BenchmarkParseDocument_Minimal-4    	  492578	      2314 ns/op	     568 B/op	      14 allocs/op
BenchmarkParseDocument_Receipt-4    	   94568	     12663 ns/op	    2392 B/op	      34 allocs/op
BenchmarkCommandUnmarshal_Text-4    	  421446	      2787 ns/op	     568 B/op	      19 allocs/op
BenchmarkCommandUnmarshal_Table-4   	  277227	      4206 ns/op	     944 B/op	      21 allocs/op
BenchmarkTextCommandParsing-4       	  524451	      2149 ns/op	     544 B/op	      16 allocs/op
BenchmarkTableCommandParsing-4      	  240616	      4984 ns/op	    1000 B/op	      29 allocs/op
BenchmarkParseHexString-4           	 8289812	       143.4 ns/op	      48 B/op	       2 allocs/op
BenchmarkCleanHexString-4           	 6656040	       179.8 ns/op	      64 B/op	       2 allocs/op
BenchmarkContainsSequence-4         	369813058	         3.274 ns/op	       0 B/op	       0 allocs/op
BenchmarkCheckCriticalCommands-4    	35282823	        37.48 ns/op	       0 B/op	       0 allocs/op
BenchmarkDocument_Validate-4       	14334823	        83.02 ns/op	       0 B/op	       0 allocs/op
BenchmarkParseDocument_Simple-4    	  498592	      2411 ns/op	     568 B/op	      14 allocs/op
BenchmarkParseDocument_Complex-4   	  138847	      8534 ns/op	    1352 B/op	      26 allocs/op
BenchmarkPrintImage_Small-4             	     573	   1955161 ns/op	 3469937 B/op	      24 allocs/op
BenchmarkPrintImage_Medium-4            	     302	   3795892 ns/op	 5481085 B/op	      24 allocs/op
BenchmarkPrintImage_ThermalPreview-4    	     135	   8769475 ns/op	 5235276 B/op	  230723 allocs/op

Base Branch Results

BenchmarkNewDocument-4    	1000000000	         0.3124 ns/op	       0 B/op	       0 allocs/op
BenchmarkBuildSimple-4    	 3641227	       336.4 ns/op	     240 B/op	       4 allocs/op
BenchmarkBuildComplex-4   	  404083	      2801 ns/op	    1809 B/op	      25 allocs/op
BenchmarkToJSON-4         	  540406	      2115 ns/op	     592 B/op	       3 allocs/op
BenchmarkParseDocument_Minimal-4    	  477943	      2414 ns/op	     568 B/op	      14 allocs/op
BenchmarkParseDocument_Receipt-4    	   90234	     13552 ns/op	    2392 B/op	      34 allocs/op
BenchmarkCommandUnmarshal_Text-4    	  406212	      2848 ns/op	     568 B/op	      19 allocs/op
BenchmarkCommandUnmarshal_Table-4   	  263967	      4372 ns/op	     944 B/op	      21 allocs/op
BenchmarkTextCommandParsing-4       	  506535	      2316 ns/op	     544 B/op	      16 allocs/op
BenchmarkTableCommandParsing-4      	  238208	      4946 ns/op	    1000 B/op	      29 allocs/op
BenchmarkParseHexString-4           	 8677948	       137.6 ns/op	      48 B/op	       2 allocs/op
BenchmarkCleanHexString-4           	 6614784	       180.3 ns/op	      64 B/op	       2 allocs/op
BenchmarkContainsSequence-4         	367252376	         3.291 ns/op	       0 B/op	       0 allocs/op
BenchmarkCheckCriticalCommands-4    	32234542	        38.82 ns/op	       0 B/op	       0 allocs/op
BenchmarkDocument_Validate-4       	14350474	        82.54 ns/op	       0 B/op	       0 allocs/op
BenchmarkParseDocument_Simple-4    	  499629	      2418 ns/op	     568 B/op	      14 allocs/op
BenchmarkParseDocument_Complex-4   	  138145	      8637 ns/op	    1352 B/op	      26 allocs/op
BenchmarkPrintImage_Small-4             	     604	   1930240 ns/op	 3469946 B/op	      24 allocs/op
BenchmarkPrintImage_Medium-4            	     319	   3729421 ns/op	 5481083 B/op	      24 allocs/op
BenchmarkPrintImage_ThermalPreview-4    	     134	   8897972 ns/op	 5235275 B/op	  230723 allocs/op

💡 Note: Use benchstat for statistical comparison

🎯 Summary

• Total Benchmarks: 32
• Average Speed: 2716616 ns/op
• Average Memory: 2396935 B/op
• Average Allocations: 41093 allocs/op