docs(memory-bank): record relay hardening policy baseline and operating knobs

memory-bank/techContext.md

@@ -22,6 +22,21 @@
 - Additional custom server entries exist (`server.js`, `server/server.js`) but are currently treated as non-active for the refactor baseline unless deployment evidence indicates otherwise.
 - Environment-driven config for auth, relay/API roots, hash key, notify key, and database URL.
 
+### Relay forwarding hardening policy knobs (P2-S3)
+
+- Shared relay middleware now enforces centralized timeout/retry behavior for relay-backed GET flows.
+- Supported env knobs:
+    - `RELAY_TIMEOUT_MS` (default `8000`, clamped `100..30000`)
+    - `RELAY_RETRY_MAX` (default `2`, clamped `0..4`)
+    - `RELAY_RETRY_BASE_DELAY_MS` (default `200`, clamped `0..5000`)
+    - `RELAY_RETRY_MAX_DELAY_MS` (default `1200`, clamped `0..5000`)
+- Retry classification:
+    - retryable: `408`, `429`, `5xx`, selected transient transport errors
+    - non-retryable: deterministic client/auth statuses (`400`, `401`, `403`, `404`, `422`) and other explicit non-retryable HTTP statuses
+- Logging behavior:
+    - structured redacted relay events emitted for retry/failure
+    - duplicate endpoint-layer error logging suppressed when relay layer already emitted terminal failure log
+
 ## Tooling and quality gates
 
 - Linting: `npm run lint` (`next lint`).