feat(studio): pass store catalog to editor + Add-module-source dialog

Two host-side pieces that complete the editor 0.18 quick-fix
loop:

  - FlowsPage now fetches the store catalog (`searchStore` with
    a 500-item ceiling) on open and hands it as `storeCapabilities`
    to the FlowEditorPage. The editor's analyzer uses it to
    decide whether an unknown-cap fix shows "Install …" or the
    Add-source alternative.

  - New `_AddModuleSourceDialog` — wired through the editor's
    `onAddModuleSource` callback. Asks the operator for a URL
    or local .fai bundle path; passes the value into
    `HubService.installModule(source: …)`. Honest about its
    limits: includes a card pointing the operator at
    `fai install --link <path>` for unpacked module source
    directories (which the gRPC install API doesn't currently
    support — that's CLI-only).

Studio bumped to 0.65.0; editor path-override pulls in 0.18.0.

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

lib/main.dart

@@ -27,7 +27,7 @@ import 'widgets/widgets.dart';
 /// Studio's own build version. Bump on every UI commit so the
 /// running app self-identifies — visible in the sidebar header
 /// and quick-glance proof that you're seeing the current build.
-const String kStudioVersion = '0.64.0';
+const String kStudioVersion = '0.65.0';
 
 Future<void> main() async {
   WidgetsFlutterBinding.ensureInitialized();