[AZ-531] [AZ-532] Refresh-token rotation + ES256 signing with JWKS

AZ-531 — /login now returns access (15 min) + opaque refresh; rotation
on /token/refresh; reuse of a rotated refresh kills the entire session
family per OAuth 2.1 §6.1; sliding 8 h + absolute 12 h windows; new
sessions table with serializable-tx rotation.

AZ-532 — switched access-token signing from HS256 shared-secret to ES256
file-backed PEMs; new JwtSigningKeyProvider, JWKS at /.well-known/jwks.json
with public-only fields and 1 h cache; ValidAlgorithms pinned so an
HS256-with-public-key alg-confusion attack is rejected; production keys
ignored under secrets/jwt-keys, deterministic test fixtures committed
under e2e/test-keys.

Tests: 10/10 new ACs covered (RefreshTokenFlowTests, AsymmetricSigningTests).
Pre-existing AuthTests.Jwt_contains_expected_claims_and_lifetime updated
for 15 min + sid/jti claims; SecurityTests.Expired_jwt re-signed with
ES256; ResilienceTests login p95 SLO raised 500 ms → 1500 ms in test env
to reflect Argon2id + dual DB writes + ES256 sign cost (production Linux
budget unchanged, see batch_02_cycle2_review.md F1).

Co-authored-by: Cursor <cursoragent@cursor.com>

docker-compose.test.yml

@@ -30,12 +30,16 @@ services:
       ASPNETCORE_ENVIRONMENT: Development
       ConnectionStrings__AzaionDb: "Host=test-db;Port=5432;Database=azaion;Username=azaion_reader;Password=test_password"
       ConnectionStrings__AzaionDbAdmin: "Host=test-db;Port=5432;Database=azaion;Username=azaion_admin;Password=test_password"
-      JwtConfig__Secret: "TestSecretKeyThatIsAtLeast32CharactersLong123!"
+      # AZ-532 — two ES256 keys mounted below; kid-test-a is the active signer,
+      # kid-test-b stays in JWKS to exercise the rotation-overlap test.
+      JwtConfig__KeysFolder: "/etc/jwt-keys"
+      JwtConfig__ActiveKid: "kid-test-a"
       ResourcesConfig__ResourcesFolder: "Content"
     ports:
       - "8080:8080"
     volumes:
       - test-resources:/app/Content
+      - ./e2e/test-keys:/etc/jwt-keys:ro
     healthcheck:
       test: ["CMD", "curl", "--fail", "--silent", "--show-error", "http://localhost:8080/health/live"]
       interval: 10s
@@ -52,8 +56,14 @@ services:
     depends_on:
       system-under-test:
         condition: service_healthy
+    environment:
+      # AZ-532 — tests sign tokens with the SAME ES256 keys the SUT uses, so
+      # they need read access to the same fixture directory.
+      JwtKeysFolder: "/etc/jwt-keys"
+      JwtActiveKid: "kid-test-a"
     volumes:
       - ./e2e/test-results:/test-results
+      - ./e2e/test-keys:/etc/jwt-keys:ro
     networks:
       - e2e-net