refactor(rules): split angular.md into index + references

Co-Authored-By: Claude Haiku 4.5 <noreply@anthropic.com>

shared/rules/angular/references/services-and-http.md

@@ -0,0 +1,40 @@
+## Dependency Injection
+
+* Prefer Angular dependency injection for application services.
+* Keep injected dependencies minimal.
+* Avoid service locator patterns.
+* Prefer `inject()` where it improves readability and is consistent with the project.
+* Do not inject services that are not used.
+* Scope services intentionally.
+* Prefer application-wide singletons only for truly shared stateless or coordinated state.
+* Avoid storing request-specific or component-specific mutable state in root services.
+* Use injection tokens for configuration or abstractions where appropriate.
+* Do not create interfaces only to satisfy dependency injection when no abstraction is needed.
+
+## Services
+
+* Keep services focused on a clear responsibility.
+* Avoid large catch-all services.
+* Separate API access, domain logic and UI state where practical.
+* Avoid leaking transport models throughout the application.
+* Do not expose mutable internal state directly.
+* Prefer readonly APIs for state consumers.
+* Avoid hidden side effects.
+* Keep service methods predictable.
+* Do not use services merely to move poorly structured component code elsewhere.
+
+## HTTP and APIs
+
+* Keep API access centralized and strongly typed.
+* Prefer dedicated API clients or data-access services.
+* Do not use `any` for API responses.
+* Treat all server responses as untrusted at runtime.
+* Validate external data when the contract is security- or correctness-critical.
+* Keep DTOs separate from domain models when their responsibilities differ.
+* Avoid duplicate API calls.
+* Cache only when the invalidation strategy is clear.
+* Avoid manual URL string construction when typed helpers or centralized endpoints are available.
+* Use interceptors only for cross-cutting concerns.
+* Do not put unrelated business logic into HTTP interceptors.
+* Handle cancellation where appropriate.
+* Handle expected error states explicitly.