refactor: Remove code duplication in internal/calculate

[adcondev]

🎯 What:

• Refactored DotsPerLine to call MmToDots in internal/calculate/calculate.go.
• Added comprehensive unit tests in internal/calculate/calculate_test.go.
• Translated comments in internal/calculate/calculate.go from Spanish to English.
• Updated LEARNING.md to include internal/calculate in the architecture overview.

💡 Why:

• DotsPerLine and MmToDots had identical logic. Consolidating them improves maintainability.
• Adding tests ensures correctness and prevents regressions.
• Translating comments improves developer experience and aligns with codebase standards.

✅ Verification:

• Ran go test ./internal/calculate/... which passed.
• Verified that DotsPerLine behaves exactly as before.

✨ Result:

• Cleaner code, better test coverage, and improved documentation.

---

PR created automatically by Jules for task 519271095584918128 started by @adcondev

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[github-actions]

👋 Thanks for opening this PR, @adcondev!

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• ✅ All tests pass
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[github-actions]

⚡ Benchmark Results

📈 Performance Comparison

📊 Click to expand detailed results

Current Branch Results

BenchmarkNewDocument-4    	1000000000	         0.3120 ns/op	       0 B/op	       0 allocs/op
BenchmarkBuildSimple-4    	 3634340	       328.0 ns/op	     240 B/op	       4 allocs/op
BenchmarkBuildComplex-4   	  411686	      2708 ns/op	    1809 B/op	      25 allocs/op
BenchmarkToJSON-4         	  546378	      2073 ns/op	     592 B/op	       3 allocs/op
BenchmarkParseDocument_Minimal-4    	  506889	      2309 ns/op	     568 B/op	      14 allocs/op
BenchmarkParseDocument_Receipt-4    	   93378	     12708 ns/op	    2392 B/op	      34 allocs/op
BenchmarkCommandUnmarshal_Text-4    	  422550	      2704 ns/op	     568 B/op	      19 allocs/op
BenchmarkCommandUnmarshal_Table-4   	  276098	      4181 ns/op	     944 B/op	      21 allocs/op
BenchmarkTextCommandParsing-4       	  529100	      2166 ns/op	     544 B/op	      16 allocs/op
BenchmarkTableCommandParsing-4      	  243658	      4862 ns/op	    1000 B/op	      29 allocs/op
BenchmarkParseHexString-4           	 8655517	       136.6 ns/op	      48 B/op	       2 allocs/op
BenchmarkCleanHexString-4           	 6715035	       178.3 ns/op	      64 B/op	       2 allocs/op
BenchmarkContainsSequence-4         	366479960	         3.242 ns/op	       0 B/op	       0 allocs/op
BenchmarkCheckCriticalCommands-4    	31214474	        39.58 ns/op	       0 B/op	       0 allocs/op
BenchmarkDocument_Validate-4       	14590293	        83.51 ns/op	       0 B/op	       0 allocs/op
BenchmarkParseDocument_Simple-4    	  502530	      2391 ns/op	     568 B/op	      14 allocs/op
BenchmarkParseDocument_Complex-4   	  139353	      8577 ns/op	    1352 B/op	      26 allocs/op
BenchmarkPrintImage_Small-4             	     582	   1980544 ns/op	 3469937 B/op	      24 allocs/op
BenchmarkPrintImage_Medium-4            	     321	   3666607 ns/op	 5481084 B/op	      24 allocs/op
BenchmarkPrintImage_ThermalPreview-4    	     138	   8601962 ns/op	 5235273 B/op	  230723 allocs/op

Base Branch Results

BenchmarkNewDocument-4    	1000000000	         0.3120 ns/op	       0 B/op	       0 allocs/op
BenchmarkBuildSimple-4    	 3613082	       330.7 ns/op	     240 B/op	       4 allocs/op
BenchmarkBuildComplex-4   	  382484	      2822 ns/op	    1809 B/op	      25 allocs/op
BenchmarkToJSON-4         	  558836	      2090 ns/op	     592 B/op	       3 allocs/op
BenchmarkParseDocument_Minimal-4    	  495026	      2350 ns/op	     568 B/op	      14 allocs/op
BenchmarkParseDocument_Receipt-4    	   92532	     12805 ns/op	    2392 B/op	      34 allocs/op
BenchmarkCommandUnmarshal_Text-4    	  421788	      2731 ns/op	     568 B/op	      19 allocs/op
BenchmarkCommandUnmarshal_Table-4   	  275132	      4251 ns/op	     944 B/op	      21 allocs/op
BenchmarkTextCommandParsing-4       	  549510	      2132 ns/op	     544 B/op	      16 allocs/op
BenchmarkTableCommandParsing-4      	  225555	      4838 ns/op	    1000 B/op	      29 allocs/op
BenchmarkParseHexString-4           	 8723923	       136.9 ns/op	      48 B/op	       2 allocs/op
BenchmarkCleanHexString-4           	 6656506	       179.6 ns/op	      64 B/op	       2 allocs/op
BenchmarkContainsSequence-4         	352499718	         3.296 ns/op	       0 B/op	       0 allocs/op
BenchmarkCheckCriticalCommands-4    	32217537	        37.51 ns/op	       0 B/op	       0 allocs/op
BenchmarkDocument_Validate-4       	14532830	        83.38 ns/op	       0 B/op	       0 allocs/op
BenchmarkParseDocument_Simple-4    	  494266	      2398 ns/op	     568 B/op	      14 allocs/op
BenchmarkParseDocument_Complex-4   	  138206	      8526 ns/op	    1352 B/op	      26 allocs/op
BenchmarkPrintImage_Small-4             	     596	   2001564 ns/op	 3469934 B/op	      24 allocs/op
BenchmarkPrintImage_Medium-4            	     312	   3839264 ns/op	 5481084 B/op	      24 allocs/op
BenchmarkPrintImage_ThermalPreview-4    	     130	   8800190 ns/op	 5235273 B/op	  230723 allocs/op

💡 Note: Use benchstat for statistical comparison

🎯 Summary

• Total Benchmarks: 32
• Average Speed: 2640073 ns/op
• Average Memory: 2396932 B/op
• Average Allocations: 41093 allocs/op