### T-21 · `Fail2BanMetadataService` has inline socket timeout hardcoded

**Where found:** `backend/app/services/fail2ban_metadata_service.py:64` — `socket_timeout: float = 5.0`

**Why this is needed:** Part of the same constant duplication as T-08. This file doesn't use `_SOCKET_TIMEOUT` as a module constant — it hardcodes `5.0` inline as a local variable. Should use the constant from `constants.py` once T-08 is done.

**Goal:** After T-08, replace with `FAIL2BAN_SOCKET_TIMEOUT_FAST` import.

**What to do:** Covered by T-08 sweep.

**Possible traps and issues:** None — dependent on T-08.

**Docs changes needed:** None.

**Doc references:** `backend/app/services/fail2ban_metadata_service.py`