test: add golden parity tests for the v1 API

Pin every endpoint's behaviour with golden fixtures captured from the
retiring grpc-gateway (timestamps and secrets neutralised). Error cases
assert their HTTP status independently of the golden via assertStatus, so
a blind regenerate cannot re-pin a wrong code; HEADSCALE_UPDATE_GOLDEN
rewrites the fixtures. A unit test exercises the API-key auth middleware
on the real server router. Exclude the emitted spec and goldens from
pre-commit checks.

.pre-commit-config.yaml

@@ -2,8 +2,9 @@
 # See: https://prek.j178.dev/quickstart/
 # See: https://prek.j178.dev/builtin/
 
-# Global exclusions - ignore generated code
-exclude: ^gen/
+# Global exclusions - ignore generated code (proto output and emitted OpenAPI)
+# and recorded golden fixtures.
+exclude: ^(gen|openapi)/|^hscontrol/testdata/apiv1_golden/
 
 repos:
   # Built-in hooks from pre-commit/pre-commit-hooks