[AZ-529] [AZ-530] Cycle-2 documentation refresh

Refreshes _docs/02_document/ to reflect the cycle-2 auth-modernization
+ CMMC hardening landings (AZ-531..AZ-538). Authoritative source for
the ripple set is ripple_log_cycle2.md.

Covered:
- architecture.md (section 1 rewritten, ADRs 6-9 added)
- data_model.md (sessions, audit_events, user columns, migrations)
- system-flows.md (F1 rewritten; F11-F17 added; F2/F7/F9 minor)
- module-layout.md (cycle-2 sub-component table)
- diagrams/flows/flow_login.md (dual-token + MFA)
- components/{01_data_layer,03_auth_and_security,05_admin_api}
- modules/ (12 new, 8 modified — full Argon2id/ES256/MFA/refresh
  /mission/session/audit/jwks rollup)
- tests/{blackbox,security,traceability-matrix}

Step 13 (Update Docs) output for cycle 2.

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

_docs/02_document/modules/services_refresh_token_service.md

@@ -0,0 +1,63 @@
+# Module: Azaion.Services.RefreshTokenService
+
+## Purpose
+Issues, rotates, and validates opaque refresh tokens for interactive sessions. Implements OAuth 2.1 §6.1 reuse-detection: presenting an already-rotated refresh token kills the entire session family.
+
+> Added in cycle 2 (2026-05-14) by AZ-531 (Epic AZ-529, Auth Mechanism Modernization). Foundation for AZ-535 (logout/revocation) and AZ-534 (MFA — pins `mfa_authenticated` to the session so refresh rotation inherits the original AMR strength).
+
+## Public Interface
+
+### IRefreshTokenService
+
+| Method | Signature | Description |
+|--------|-----------|-------------|
+| `IssueForNewLogin` | `Task<(string OpaqueToken, Session Session)> IssueForNewLogin(Guid userId, bool mfaAuthenticated = false, CancellationToken ct = default)` | Mint a fresh refresh token at login; starts a new session family. The opaque token is returned to the caller; only its SHA-256 hash is persisted. `mfaAuthenticated` is pinned to the session row so rotation preserves AMR strength. |
+| `Rotate` | `Task<(string OpaqueToken, Session Session)> Rotate(string opaqueToken, CancellationToken ct = default)` | Rotate the supplied refresh token. On success returns a new opaque token + the new session row. Throws `BusinessException(InvalidRefreshToken)` on bad/expired/revoked input; on reuse-detection (already-rotated token presented again) the entire session family is revoked first. |
+
+## Internal Logic
+
+- **Token format**: 32 random bytes (256 bits) base64url-encoded → 43-char string (no padding). Persisted as the SHA-256 hex digest in `sessions.refresh_hash`. The opaque value is never logged.
+- **Family semantics**: each `IssueForNewLogin` creates a new family (`family_id == id`). Each `Rotate` inserts a new row in the same family with `parent_session_id` chained to the previous row, then marks the previous row `revoked_reason='rotated'`.
+- **Reuse detection**: if a presented token is found with `revoked_reason='rotated'`, every active row in the same family is set to `revoked_reason='reuse_detected'` (per OAuth 2.1 §6.1) — even the row that succeeded last cycle stops working.
+- **Sliding expiry**: each rotation moves `expires_at` to `now + RefreshSlidingHours` (default 8 h).
+- **Absolute cap**: a family older than `RefreshAbsoluteHours` (default 12 h) since `family_started_at` is rejected even if every individual rotation stayed within the sliding window.
+- **Concurrency**: rotation runs in a `Serializable` transaction so two concurrent refreshes of the same token can't both succeed.
+
+## Dependencies
+
+- `IDbFactory` — admin connection for inserts/updates
+- `IOptions<SessionConfig>` — sliding/absolute window TTLs (defined alongside `JwtConfig` in `Azaion.Common/Configs/JwtConfig.cs`)
+- `Session` entity, `SessionRevokedReasons` constants
+- `BusinessException` / `ExceptionEnum.InvalidRefreshToken`
+- `System.Security.Cryptography.RandomNumberGenerator` + `SHA256`
+
+## Consumers
+
+- `Program.cs` `/login` → calls `IssueForNewLogin` after `UserService.ValidateUser` succeeds
+- `Program.cs` `/login/mfa` → calls `IssueForNewLogin` after MFA second factor
+- `Program.cs` `/token/refresh` → calls `Rotate`
+
+## Data Models
+
+Operates on the `Session` entity via `AzaionDb.Sessions` table.
+
+## Configuration
+
+`SessionConfig` (bound from `appsettings.json` section `SessionConfig`):
+- `RefreshSlidingHours` (default 8)
+- `RefreshAbsoluteHours` (default 12)
+
+## External Integrations
+
+PostgreSQL via `IDbFactory`.
+
+## Security
+
+- Refresh tokens are opaque random strings, never JWTs — verifiers cannot decode or alter them.
+- The plaintext token leaves the server only at issue/rotation; the DB stores only the SHA-256 hash.
+- Reuse-detection is the primary defence against stolen-refresh-token attacks: the legitimate user's next refresh will be rejected and they'll be forced to re-authenticate, but the attacker's token also dies.
+- Rotation is transactional (`Serializable`) so concurrent refresh races cannot leak two valid descendants.
+
+## Tests
+
+- `e2e/Azaion.E2E/Tests/RefreshTokenTests.cs` — covers AC-1 (login dual tokens), AC-2 (rotation invalidates old), AC-3 (reuse kills family), AC-4 (sliding + absolute expiry), AC-5 (opaque, not JWT).