feat(local-identity): Stage 3 — minimal native OIDC provider (NK-WP-0002-T03)

Add local-identity serve command: a minimal Authorization Code flow OIDC
server backed by file-store users.  Implemented natively with no heavy
OIDC library — only stdlib http.server and the cryptography package.

New modules:
  keys.py      RSA-2048 signing key generation + JWKS helpers
  tls.py       Self-signed TLS certificate (localhost/127.0.0.1 SANs)
  jwt_utils.py RS256 JWT creation and verification
  serve.py     OIDCHandler + make_handler() factory + run_server()

Endpoints: /.well-known/openid-configuration, /jwks, /auth, /token,
/userinfo.  Server binds to 127.0.0.1 only; tokens carry iss: local-identity
which production Keycloak rejects by design.

104 tests passing (16 new for Stage 3).

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

local-identity/pyproject.toml

@@ -5,6 +5,7 @@ description = "Zero-dependency bootstrap user store for net-kingdom environments
 requires-python = ">=3.11"
 dependencies = [
     "pyyaml>=6.0",
+    "cryptography>=42.0",
 ]
 
 [project.scripts]