Add Tampermonkey userscript generator for permanent Fluidd panel

Adds a 'Tampermonkey script' button in the footer that prompts for the
Fluidd URL, generates a ready-to-paste userscript with CFSYNC_URL and
@match pre-filled, and copies it to clipboard. The userscript auto-loads
the CFS panel on every Fluidd page visit without needing to click a bookmarklet.

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>