feat: fai_dart_sdk scaffold

Dart package skeleton for the F∆I gRPC client. Used by F∆I
Studio (Tier-2) and Tier-3 domain apps (DigiScout / J∆I /
Scout). Public surface — HubClient, HubEndpoint — is committed
as a typed stub so downstream apps can compile against it
immediately. Generated proto bindings land in a follow-up
commit once the codegen step (planned: tools/generate.sh
wrapping protoc-gen-dart against ../fai_platform/proto) is
wired in.

Future Forgejo path: fai/dart-sdk.

dart analyze: clean. dart test: 4/4.

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

pubspec.yaml

@@ -0,0 +1,16 @@
+name: fai_dart_sdk
+description: gRPC client SDK for the F∆I Platform hub. Used by F∆I Studio and Tier-3 domain apps.
+version: 0.1.0
+publish_to: 'none'
+repository: https://git.flemming.ws/fai/dart-sdk
+
+environment:
+  sdk: ^3.11.0-200.1.beta
+
+dependencies:
+  grpc: ^4.0.0
+  protobuf: ^4.0.0
+
+dev_dependencies:
+  lints: ^6.0.0
+  test: ^1.25.6