feat(settings): multi-version uninstall picker + default_scope editor

Two operator surfaces shipped together:

**Multi-version uninstall picker** — when more than one version
of a `(provider, name)` is installed side-by-side, both the
module-sheet "Uninstall" affordance and the store-detail
"Uninstall" affordance now ask the operator which version to
remove before calling the RPC. The hub's wire-level support for
this (UninstallModuleRequest.version) was already there; Studio
just wasn't using it. Picker pre-selects the highest version so
single-version flows still take one click.

  - `HubService.installedVersions(name)` enumerates the installed
    versions via the capabilities list.
  - `HubService.uninstallModule(name, version: ...)` forwards
    the version into the RPC.
  - `_UninstallVersionPickerDialog` (module sheet) and
    `_StoreUninstallVersionPickerDialog` (store) host the
    picker — separate widgets so each surface can evolve copy
    independently. Uses `RadioGroup<String>` for Flutter
    3.32+ deprecation compliance.

**Default scope editor** — new DEFAULT SCOPE panel in Settings
that calls the freshly-added HubAdmin RPCs
`GetDefaultScope` / `SetDefaultScope`. Operators can:

  - reorder publisher segments with up/down buttons
    (first match wins in the bare-form resolver),
  - delete entries (hub still rejects empty list — Studio
    surfaces the constraint inline),
  - add arbitrary entries via the text field,
  - add catalog-known publishers via suggestion chips
    (sorted alphabetically, populated from the catalog).

Every change persists to `~/.fai/config.yaml` via the hub
and hot-swaps the in-memory copy without a daemon restart.

Bumped pubspec to 0.48.0. dart analyze clean (No issues
found!); flutter test green (11 tests).

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: 0.47.1
+version: 0.48.0
 
 environment:
   sdk: ^3.11.0-200.1.beta