follow-up: update SECURITY.md Linux fallback language after upstream #988 merges

[yasinBursali]

Context

Upstream PR Light-Heart-Labs/DreamServer#988 changes the Linux Docker-bridge-gateway detection fallback in `bin/dream-host-agent.py` from `0.0.0.0` to `127.0.0.1` (security fix: prevents LAN exposure when bridge detection fails).

Meanwhile, PR Light-Heart-Labs/DreamServer#973 (docs sync) is independently mergeable because its `SECURITY.md` Linux row currently matches the pre-Light-Heart-Labs#988 code: "Falls back to `0.0.0.0` if detection fails."

Once Light-Heart-Labs#988 merges, that one sentence in `dream-server/SECURITY.md` (around line 86, in the "Host Agent Network Binding" table) becomes stale by a single phrase.

Fix

One-line doc edit after Light-Heart-Labs#988 lands on `main`:
```diff

• | Linux | auto-detected | ... Falls back to `0.0.0.0` if detection fails. |

• | Linux | auto-detected | ... Falls back to `127.0.0.1` if detection fails. |
  ```

Can either be a tiny follow-up PR or folded into a future docs batch. Should be trivial.

Priority

Low — accurate-by-default descriptions of fallback behavior are nice to have, but the fallback path is rare (only fires when Docker bridge detection fails entirely). Not urgent.

[yasinBursali]

Addressed in upstream PR Light-Heart-Labs#1017. (Draft pending upstream Light-Heart-Labs#988+Light-Heart-Labs#973 merge.)