Organize unit tests into modular structure following 42 norms

[Copilot]

The repository had confusing example tests mixed into src/main.c with no organized test suite. Tests need to follow 42 School coding standards (max 5 functions per file, norminette compliance).

Changes

Test Infrastructure

• Created /tests directory with module-based organization mirroring src/ structure
• Built test runner with color-coded output and per-module test grouping
• Split tests across 19 files to comply with 5-function limit

Test Coverage

Added 40+ unit tests covering:

• Memory: memset, bzero, memcpy, memmove, memchr, memcmp, calloc
• Strings: strlen, strchr, strrchr, strncmp, strcmp, strnstr, strdup, substr, strjoin, strtrim, split
• Converts: atoi, itoa, toupper, tolower
• Ctype: isalpha, isdigit, isalnum, isascii, isprint, isupper, islower, issign
• Lists: lstnew, lstadd_front, lstadd_back, lstsize
• Prints: printchar, printstr, printf, printbool
• Files: isfile
• Debug: debug_mode

Build System

• Updated test.mk to compile all test modules
• Fixed targets.mk to include missing ft_tknlen and ft_tkncount (required by ft_split)
• Replaced src/main.c with informative message pointing to new test suite

Run tests with make test or make t. All files pass norminette validation.

Original prompt

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This section details on the original issue you should resolve

<issue_title>Make usefull tests</issue_title>
<issue_description>Create useful unit tests in folder /tests

Remove confusing tests, separate them into more readable and organized tests.

Divide them by different c files and different folders.</issue_description>

<agent_instructions>Follow 42 norms. Use norminette to validate it ;)</agent_instructions>

Comments on the Issue (you are @copilot in this section)

• Fixes Make usefull tests #29

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