feat(decky): visible branded Steam shortcut, one-tap client updates, fullscreen-page polish

- The "Punktfunk" shortcut is no longer hidden: it now ships committed
  artwork (grid/wide/hero/logo/icon, generated by scripts/gen-steam-art.py
  — a pure-stdlib SDF renderer drawing the lens mark + a monoline
  "punktfunk" wordmark) applied via SetCustomArtworkForApp /
  SetShortcutIcon. Existing installs are unhidden and re-arted once per
  ART_VERSION; relaunching the library entry streams to the last host.
- Updates cover the flatpak CLIENT too: check_update compares the
  user-scope installed commit against its remote, applyUpdate runs
  `flatpak update --user` first (awaited) and the plugin reinstall —
  which reloads the panel — last; docs spell out the sudo-less --user
  update ("sudo flatpak update" silently skips per-user installs).
- Fullscreen page: DialogButton stretches to 100% width in the gamepad
  UI, so the Stream/Pair/Refresh/… actions filled whole rows — sized to
  content + right-aligned now; the header drops its Update button (About
  tab + QAM banner keep the flow) and the back button gets a real 40px
  hit target.
- Settings: the disable-Steam-Input note also shows for Automatic — on a
  Deck that now forwards the built-in controller as a Steam Deck pad
  (paddles/trackpads/gyro), which needs Steam Input off for the shortcut.

Co-Authored-By: Claude Fable 5 <noreply@anthropic.com>

docs-site/content/docs/install-client.md

@@ -34,10 +34,11 @@ flatpak install --user https://flatpak.unom.io/io.unom.Punktfunk.flatpakref
 flatpak run io.unom.Punktfunk
 ```
 
-Updates, from then on:
+Updates, from then on — **without `sudo`** (this is a `--user` install; `sudo flatpak update` only
+touches the *system* scope and silently skips it):
 
 ```sh
-flatpak update                       # or: flatpak update io.unom.Punktfunk
+flatpak update                       # or: flatpak update --user io.unom.Punktfunk
 ```
 
 Prefer your native package manager? The client also ships as real packages (add the repo once —