feat: implement forward search functionality

[rayworks]

• Implement search_fwd() function in ted_buffer.c

  • Search from current cursor position forward through buffer
  • Move cursor to first match found

• Add search command to ted_commands.c

  • Prompt user for search keyword
  • Integrate with search_fwd() function

• Add ctrl+r keybinding for search in ted_input.c

• Add command hints for search functionality