Phase A: generierter Dart-Client + DI-Foundation für Rust-Backend

OpenAPI-Generator-Setup:
- tool/generate_api_client.sh: Direkter Aufruf der openapi-generator-cli.jar
  (Java-CLI statt Dart-build_runner-Integration — vermeidet die
  analyzer-/source_gen-Version-Hölle mit json_serializable)
- tool/fetch_openapi_generator.sh: lädt die JAR (29 MB) nach (gitignored)
- openapi/holzleitner.json: Snapshot der Backend-Spec für reproduzierbare
  Generation
- packages/holzleitner_api/: generiertes Dart-Sub-Package (built_value +
  dio), per path-dep im Haupt-pubspec eingehängt

Netzwerk-Layer (lib/data/network/):
- BackendConfig: API- und Keycloak-Endpoints für Local-Dev (localhost
  wegen Keycloak-iss-Claim).
- AuthTokenProvider-Schnittstelle.
- DevPasswordGrantTokenProvider: Phase-A-Provider via Keycloak
  password-grant, Token-Caching mit Expiry-Check (Phase B ersetzt das
  durch flutter_appauth PKCE).
- HolzleitnerAuthInterceptor: dynamischer Bearer-Inject pro Request.
- HolzleitnerApiFactory: baut die generierte HolzleitnerApi-Klasse
  mit unserem Interceptor statt der vier Default-Auth-Interceptors.
- network_locator.registerNetworking(): get_it-Setup, in main() vor
  runApp() aufgerufen.

Clean-Arch-Scaffolding (lib/data/, lib/domain/):
- Verzeichnisstruktur für Phase C+D angelegt (mapper/, repository/,
  entity/, repository/) — befüllt sich in den Folge-Phasen.

Smoke-Test:
- tool/smoke_test_api.dart ruft /health (ungeschützt) und /me/cars
  (mit Bearer) via generiertem Client — grün gegen lokales Backend.

packages/holzleitner_api/.gitignore

@@ -0,0 +1,41 @@
+# See https://dart.dev/guides/libraries/private-files
+
+# Files and directories created by pub
+.dart_tool/
+.buildlog
+.packages
+.project
+.pub/
+build/
+**/packages/
+
+# Files created by dart2js
+# (Most Dart developers will use pub build to compile Dart, use/modify these
+#  rules if you intend to use dart2js directly
+#  Convention is to use extension '.dart.js' for Dart compiled to Javascript to
+#  differentiate from explicit Javascript files)
+*.dart.js
+*.part.js
+*.js.deps
+*.js.map
+*.info.json
+
+# Directory created by dartdoc
+doc/api/
+
+# Don't commit pubspec lock file
+# (Library packages only! Remove pattern if developing an application package)
+pubspec.lock
+
+# Don’t commit files and directories created by other development environments.
+# For example, if your development environment creates any of the following files,
+# consider putting them in a global ignore file:
+
+# IntelliJ
+*.iml
+*.ipr
+*.iws
+.idea/
+
+# Mac
+.DS_Store