v2.2.0 — Configurator + Builder UX overhaul

Big UX pass on the Configurator + Builder, plus a hotfix for a freeze
that hit Library uploads / rotate-flip on multi-MB images.

Configurator

• Vertical section sidebar (sticky) replaces the horizontal nav row.
• 📺 Vorschau toggle in the header pops a floating live preview
  (its own iframe instance — doesn't fight the Widgets-tab inline preview).
• Look-tab: new Bildschirm-Layout card (span / mirror / reset live
  here, gear hidden); current-background thumbnail tile.
• Library tab right-click context menu: apply / rotate / flip /
  pin / rename / duplicate / delete. Rotate + flip use PIL server-side
  and propagate to main + thumb + 4K siblings together.
• Integrations tab: System stays open by default, each integration
  (OpenRGB output, OpenRGB SDK server, per-screen colour source, sACN /
  E1.31, MQTT, REST API, plugins) collapses into its own <details> block.

Builder

• New Apply ▾ button in the canvas toolbar — picks a bridge screen +
  stretch / span-split target. Skips the full Monitor-Wall flow for
  single-image edits.
• Wall tiles for span screens crop to the per-tile sub-region
  instead of repeating the full bridge background in every tile.
• Drag-into-canvas always lands in the editor (the
  Editor / split-across-span popup is gone).
• "Choose image…" button visible in Simple mode too.

Branding

• Inline SVG header logo + matching favicon (monitor + 5 RGB pads,
  mirrors the tray icon) on both Configurator + Builder pages.

Fixes

• Configurator froze for ~1 min during Library uploads with Auto-Cut
  and during rotate / flip — PIL ops + _library_rebuild_catalogue
  now run in a thread executor instead of blocking the asyncio loop.
  WebP encoder dropped from method=6 → method=4 (~5× faster, same
  visual quality for wallpapers).

Upgrade notes

• Wallpaper bundle re-import is required this release —
  wallpaper/index.html shipped the in-page widget picker removal.
  Lively / Wallpaper Engine users should re-import after installing.