chore(deps): grpc 4→5, protobuf 4→6

Two coupled majors that have been blocking the rest of the
Dart-side dependency lift in Studio (the constraint solver
pins meta/characters/etc. through these). Picked up:

- grpc 5.1.0 (was 4.2.0)
- protobuf 6.0.0 (was 4.2.0)
- analyzer 13.0.0, _fe_analyzer_shared 100.0.0
- google_cloud 0.5.0, googleapis_auth 2.3.1 (transitive)

The bindings now live in `lib/src/generated/fai/v1/` only —
the well-known-types `lib/src/generated/google/protobuf/`
copy has been deleted. protobuf 6 ships its own bundled
`well_known_types/google/protobuf/empty.pb.dart` and the
`HubAdminClient` API expects the *packaged* Empty type;
emitting a local copy created two distinct Empty types and
broke every `_admin.<rpc>(Empty())` call site.

`tools/generate.sh` now skips the WKT generation pass and
wipes `lib/src/generated/google/` on every run so the
duplicate-types breakage can't regress silently. The
import in `hub_client.dart` switches from the local copy to
`package:protobuf/well_known_types/google/protobuf/empty.pb
.dart`.

Smoke-verified: dart analyze clean, dart test green
(4 tests). Bumped to 0.17.0 — Studio absorbs in the next
commit.

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

pubspec.yaml

@@ -1,6 +1,6 @@
 name: fai_client_sdk
 description: gRPC client SDK for the F∆I Platform hub. Used by F∆I Studio and Tier-3 domain apps.
-version: 0.16.0
+version: 0.17.0
 publish_to: 'none'
 repository: https://git.flemming.ai/fai/client-sdk-dart
 
@@ -8,8 +8,8 @@ environment:
   sdk: ^3.11.0-200.1.beta
 
 dependencies:
-  grpc: ^4.0.0
-  protobuf: ^4.0.0
+  grpc: ^5.0.0
+  protobuf: ^6.0.0
   fixnum: ^1.1.0
 
 dev_dependencies: