feat(studio): channel switcher, autostart toggle, Store redesign (v0.18.0)

UI parity for operators who never touch a CLI, plus a Store
that reads more like an app store.

Settings dialog:
- Channel rows gain a popup menu: Connect / Make active /
  Enable autostart / Disable autostart. "Connect" still
  re-points Studio's wire; "Make active" actually writes
  ~/.fai/current-channel via `fai channel switch`.
- Inline output panel surfaces the spawned binary's stdout
  on success or stderr on failure, so operators see what
  happened without opening a terminal.

Store page rewrite:
- Big top search bar with a clear button. Live filter on
  every keystroke.
- Horizontal category strip auto-populated from the index;
  segmented status row (All / Published / Alpha / Planned),
  Installed-only chip, result count.
- Grid of cards that reflows to fit the viewport — replaces
  the previous single-column list. Each card shows
  category-aware icon, version, status, tagline preview, and
  a one-click Install (or Details for installed / planned).
- Per-module detail sheet renders the full bilingual
  description with a DE/EN toggle, separate Required-
  capabilities + Required-host-services sections, repo link,
  Read-docs button. Install + Uninstall live at the bottom.
- StoreItem and HubService.searchStore now carry the German
  tagline + description so the locale toggle has something
  to switch to.

SystemActions extended with `faiChannelSwitch`,
`faiDaemonEnable`, `faiDaemonDisable` so Settings can spawn
the right CLI without each call site reimplementing the
`fai` resolution rules.

Signed-off-by: flemming-it <stefan.a.flemming@googlemail.com>

pubspec.yaml

@@ -1,7 +1,7 @@
 name: fai_studio
 description: "F∆I Studio — desktop GUI for the F∆I hub"
 publish_to: 'none'
-version: 0.17.0
+version: 0.18.0
 
 environment:
   sdk: ^3.11.0-200.1.beta