Add -v/--version flag to ushow and uterm

[koldunovn]

Summary

• Adds -v/--version CLI flag to both ushow and uterm, printing ushow 0.1.3 / uterm 0.1.3 and exiting
• Defines USHOW_VERSION constant in src/us_types.h for centralized version management
• Updates README usage sections for both tools

Closes #21

Test plan

• make clean && make compiles without errors
• ./ushow -v prints ushow 0.1.3
• ./uterm -v prints uterm 0.1.3
• ./ushow --version prints ushow 0.1.3
• ./ushow -h includes -v, --version in help output

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