feat: add module structure system for customizable output

[unhappychoice]

Summary

Add --structure option to customize which modules are displayed and in what order, inspired by fastfetch.

Available Modules

Module	Description
Title	username@Steam
Separator	Horizontal line
Member	Account age in years
Level	Steam level
Games	Total games owned
Unplayed	Unplayed games count and %
Playtime	Total playtime in hours
Perfect	Perfect games count
Achievements	Total achievements and %
TopPlayed	Top played games list
RecentlyPlayed	Recently played (2 weeks)
Rarest	Rarest achievement
Break	Empty line
Colors	Color palette blocks

Interface

# Show only specific modules
steamfetch --structure "Title:Separator:Level:Games:Playtime"

# Minimal output
steamfetch --structure "Title:Games:Playtime"

# Full output with breaks
steamfetch --structure "Title:Separator:Member:Level:Games:Unplayed:Playtime:Perfect:Achievements:Break:TopPlayed:Break:RecentlyPlayed:Break:Rarest"

Implementation

• Parse --structure string into module list
• Create trait Module with render() method
• Implement each module as a struct
• Default structure matches current output

[linear]

E-775