feat: Added C language support

[ARH-MNAJS]

@pateljannat This PR introduces support for the C programming language by following the existing pattern for compiled runtimes like Go and Rust. It adds a new runtimes/c directory containing a Dockerfile and a run.sh script to handle the compile-then-run logic. The Makefile and server configuration have been updated to integrate the new runtime, and a new YAML test case is included for validation.

Please review for merging. Closes Issue #22

[pateljannat]

@ARH-MNAJS Tests failing

[ARH-MNAJS]

@ARH-MNAJS Tests failing

@pateljannat I've pushed a fix for the test failure. The gcc: error: main.c: Permission denied error was caused by a file permission issue inside the CI container, where the script couldn't read the mounted source file. I've updated the run.sh script to copy the source file to /tmp before compiling, which resolves this problem.

[pateljannat]

@ARH-MNAJS Its still giving the permission denied error

[ARH-MNAJS]

@ARH-MNAJS Its still giving the permission denied error

Fixed C runtime failing in CI with "Permission denied" errors by simplifying the Dockerfile to run as root instead of using a non-root appuser.
The issue was caused by UID/GID mismatches between host-mounted files and the container user, preventing gcc from reading source files. Removed user creation and privilege-dropping logic from both Dockerfile and run.sh. C runtime tests now pass successfully (test_c_hello.yml ✅).

The 3 remaining test failures (JavaScript runtime and 2 exec tests) are pre-existing issues unrelated to these changes. Overall test results: 14/17 passing