feat(powershell): add optional cyberpunk theme with dashboard

[HEO-80]

Add optional Cyberpunk theme for PowerShell

This PR adds an optional cyberpunk-themed layer to the existing PowerShell setup.

Zero breaking changes — activation requires uncommenting a single line in user_profile.ps1. Everything reverts by commenting it back.

What it adds

• Startup dashboard — System Info, shortcuts, installed features and live Docker container status
• NETWATCH Oh My Posh theme — prompt with git branch, path, user and execution time
• Write-Cyber helper — write any hex color via ANSI in PowerShell
• Global color palette — restyle everything by editing 6 hex values
• help-ps command — full reference of tools, shortcuts and functions

What it does NOT change

• EditMode Emacs — preserved
• Ctrl+F / Ctrl+R fzf chords — preserved
• All existing aliases (g, ll, vim, grep, tig, less) — preserved
• $env:GIT_SSH and PATH — preserved
• posh-git module — preserved

Activation

Uncomment the last line in user_profile.ps1:

. "$PSScriptRoot\themes\cyberpunk\cyberpunk.ps1"

Full standalone version: HEO-80/powershell-cyberpunk