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>

lib/widgets/fai_module_sheet.dart

@@ -50,11 +50,32 @@ class _FaiModuleSheetState extends State<FaiModuleSheet> {
 
   Future<void> _confirmAndUninstall(ModuleDetail detail) async {
     final l = AppLocalizations.of(context)!;
+    // When more than one version of the same module is
+    // installed side-by-side, ask the operator which one to
+    // remove. The hub's uninstall RPC otherwise falls back to
+    // "remove the highest version", which is rarely what an
+    // operator means when they've explicitly kept multiple
+    // versions around.
+    final versions =
+        await HubService.instance.installedVersions(detail.name);
+    if (!mounted) return;
+    String? targetVersion;
+    if (versions.length > 1) {
+      targetVersion = await showDialog<String>(
+        context: context,
+        builder: (ctx) => _UninstallVersionPickerDialog(
+          moduleName: detail.name,
+          versions: versions,
+        ),
+      );
+      if (targetVersion == null || !mounted) return;
+    }
+    final displayVersion = targetVersion ?? detail.version;
     final ok = await showDialog<bool>(
       context: context,
       builder: (ctx) => AlertDialog(
         title: Text(l.modulesUninstallTitle),
-        content: Text(l.modulesUninstallBody(detail.name, detail.version)),
+        content: Text(l.modulesUninstallBody(detail.name, displayVersion)),
         actions: [
           TextButton(
             onPressed: () => Navigator.pop(ctx, false),
@@ -74,7 +95,10 @@ class _FaiModuleSheetState extends State<FaiModuleSheet> {
     if (ok != true || !mounted) return;
     setState(() => _uninstalling = true);
     try {
-      final r = await HubService.instance.uninstallModule(detail.name);
+      final r = await HubService.instance.uninstallModule(
+        detail.name,
+        version: targetVersion ?? '',
+      );
       if (!mounted) return;
       ScaffoldMessenger.of(context).showSnackBar(
         SnackBar(
@@ -299,6 +323,85 @@ class _Body extends StatelessWidget {
   }
 }
 
+/// Modal that asks the operator to pick which installed
+/// version to uninstall when more than one version of the same
+/// `(provider, name)` is on disk side-by-side. Pops the picked
+/// version string, or `null` on cancel.
+class _UninstallVersionPickerDialog extends StatefulWidget {
+  final String moduleName;
+  final List<String> versions;
+
+  const _UninstallVersionPickerDialog({
+    required this.moduleName,
+    required this.versions,
+  });
+
+  @override
+  State<_UninstallVersionPickerDialog> createState() =>
+      _UninstallVersionPickerDialogState();
+}
+
+class _UninstallVersionPickerDialogState
+    extends State<_UninstallVersionPickerDialog> {
+  late String _picked;
+
+  @override
+  void initState() {
+    super.initState();
+    // Default to the highest version — same fallback the hub
+    // would pick without an explicit version, so the operator
+    // can confirm with one click in the common case.
+    _picked = widget.versions.last;
+  }
+
+  @override
+  Widget build(BuildContext context) {
+    final l = AppLocalizations.of(context)!;
+    return AlertDialog(
+      title: Text(l.uninstallVersionPickerTitle),
+      content: Column(
+        crossAxisAlignment: CrossAxisAlignment.start,
+        mainAxisSize: MainAxisSize.min,
+        children: [
+          Text(l.uninstallVersionPickerBody(widget.moduleName)),
+          const SizedBox(height: FaiSpace.md),
+          RadioGroup<String>(
+            groupValue: _picked,
+            onChanged: (val) {
+              if (val != null) setState(() => _picked = val);
+            },
+            child: Column(
+              mainAxisSize: MainAxisSize.min,
+              children: [
+                for (final v in widget.versions)
+                  RadioListTile<String>(
+                    value: v,
+                    title: Text(
+                      'v$v',
+                      style: const TextStyle(fontFamily: 'monospace'),
+                    ),
+                    dense: true,
+                    contentPadding: EdgeInsets.zero,
+                  ),
+              ],
+            ),
+          ),
+        ],
+      ),
+      actions: [
+        TextButton(
+          onPressed: () => Navigator.pop(context),
+          child: Text(l.buttonCancel),
+        ),
+        FilledButton(
+          onPressed: () => Navigator.pop(context, _picked),
+          child: Text(l.uninstallVersionPickerContinue),
+        ),
+      ],
+    );
+  }
+}
+
 class _SectionHeader extends StatelessWidget {
   final String text;