Implement In-Memory Filesystem Using Tree of struct inode

Implement in-memory filesystem with inode tree structure.

Requirements:

• Define inode structure with metadata and data
• Define dentry structure for directory entries
• Maintain root directory inode
• Implement fs_create(path, content) to create files
• Implement fs_read(path, buffer, size) to read files
• Implement fs_ls(path) to list directory contents
• Implement fs_mkdir(path) to create directories
• Support nested paths (e.g., /home/user/docs/file.txt)
• Print each operation (create, read, list)
• Handle errors (file not found, directory not found)
• Demonstrate creating files in multiple directories