feat(endpoint): add tests and mark tasks 1-7 as completed

- Add 7 registry tests (handler_registry_*) to registry.rs
- Add 4 dispatch tests (build_auth_context_*, dispatch_decision_logic_*) to dispatch.rs
- Add 6 endpoint tests to endpoint.rs:
  - debug_for_alknet_endpoint_is_implemented_without_panicking
  - endpoint_constructs_with_iroh_raw_key_identity (adapted for new API)
  - iroh_endpoint_runs_accept_loop_and_shutdown (adapted for new API)
  - with_iroh_sets_field (replaces has_iroh_identity_true_for_raw_key)
  - without_iroh_field_is_none (replaces has_iroh_identity_false_for_x509)
  - endpoint_works_without_iroh (replaces has_iroh_identity_false_when_no_identity)
- Add async-trait as dev-dependency
- All 17 tests pass with iroh feature
- All 8 tests pass without features
- Workspace tests all pass (no breakage)
- Mark tasks 1-7 as completed

Cargo.lock

@@ -103,6 +103,7 @@ version = "0.1.0"
 dependencies = [
  "alknet-core",
  "arc-swap",
+ "async-trait",
  "iroh",
  "quinn",
  "rustls",