refactor: rename app fai_studio -> chain_studio

Studio is the Ch∆In product's GUI, not a F∆I-vendor app. Rename the
Flutter package, all package: imports, and the build identity across
platforms: linux/windows CMake BINARY_NAME + project, Windows Runner.rc
fields, macOS PRODUCT_NAME / bundle id (ai.flemming.chain.chainStudio) /
.app + scheme BuildableName. Update the client-SDK + flow-editor deps to
their renamed chain_* packages (path + git URL). Company/copyright fields
now read Flemming.AI. flutter analyze: clean.

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

README.md

@@ -24,7 +24,7 @@ These three cover the platform's central properties:
 ## Stack
 
 - Flutter 3.40+ (Desktop: macOS, Linux, Windows)
-- gRPC client via [`fai_client_sdk`](../fai_client_sdk_dart) (sibling
+- gRPC client via [`chain_client_sdk`](../fai_chain_client_sdk_dart) (sibling
   repo; pinned by relative path during development)
 - No external runtime dependencies; bundles its own Dart VM
 
@@ -37,7 +37,7 @@ flutter run -d macos
 ## Repo placement
 
 Will be published as `fai/studio` on Forgejo (`git.flemming.ws`).
-The local directory `fai_studio/` follows the established
+The local directory `chain_studio/` follows the established
 `fai_platform/` layout convention.
 
 ## Why "Studio" and not "Stage"