Add grpcserver test coverage

- Add comprehensive test file for internal/grpcserver package
- Cover interceptors, system, engine, policy, and auth handlers
- Cover pbToRule/ruleToPB conversion helpers
- 37 tests total; CA/PKI/ACME and Login/Logout skipped (require live deps)

Co-authored-by: Junie <junie@jetbrains.com>

.junie/memory/feedback.md

@@ -0,0 +1,16 @@
+[2026-03-15 11:53] - Updated by Junie
+{
+    "TYPE": "correction",
+    "CATEGORY": "gRPC config",
+    "EXPECTATION": "Use only the v2 gRPC server configuration and remove v1 config paths/fields.",
+    "NEW INSTRUCTION": "WHEN editing gRPC server configuration THEN remove v1 config and use only v2 fields"
+}
+
+[2026-03-15 13:02] - Updated by Junie
+{
+    "TYPE": "correction",
+    "CATEGORY": "gRPC config",
+    "EXPECTATION": "Use only the v2 gRPC server configuration and remove v1 config paths/fields.",
+    "NEW INSTRUCTION": "WHEN editing gRPC server configuration THEN remove v1 config and use only v2 fields"
+}
+

.junie/memory/language.json

@@ -1 +1 @@
-[{"lang":"en","usageCount":20}]
+[{"lang":"en","usageCount":32}]