docs(adr): ADR-0018 — client-side noise suppression, opt-in and self-hosted

sorb's decision after the prototype: integrate DeepFilterNet3 as a LiveKit track
processor, off by default, assets fetched only when the user enables it, checkbox
plus slider, 35 percent default.

Opt-in is what makes the 23.3 MB affordable — only those who benefit pay for it.
Three of the source specification's assumptions did not survive measurement and are
recorded as rejected alternatives: the dry/wet mixer (the model limits attenuation
natively, and mixing raw signal back would return the keystrokes), the Rust/wasm
build (a maintained package makes it unnecessary), and loading assets from the
vendor CDN (every participant's IP to a third party at call start).

Mobile stays untested by choice; since the filter is opt-in it simply stays off on
weak devices, so that is a follow-up rather than a blocker.

Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>

STATUS.md

@@ -34,7 +34,7 @@ Verteilung: M1 5 · M2 12 · M4 3 · M5 1
 
 _none active_
 
-## ADRs (17)
+## ADRs (18)
 
 | ADR | Status | Title |
 |---|---|---|
@@ -55,6 +55,7 @@ _none active_
 | [0015](docs/adr/0015-wiki-git-storage-ueber-gitea-kanonisieren.md) | accepted | 0015 — Wiki.js Git-Storage: Inhalt fließt Cluster→Gitea→kanonisiert nach git.lab |
 | [0016](docs/adr/0016-notfallhandbuch-nicht-spiegeln.md) | accepted | 0016 — Das Notfallhandbuch bleibt lab-intern und wird nicht gespiegelt |
 | [0017](docs/adr/0017-split-dns-cfgmon-vier-zonen.md) | accepted | 0017 — Split-DNS auf CFGMON: vier Zonen statt einer, je Zone begründet |
+| [0018](docs/adr/0018-ki-geraeuschunterdrueckung-clientseitig-opt-in.md) | accepted | 0018 — KI-Geräuschunterdrückung in threadnet-call: client-seitig, opt-in, selbst ausgeliefert |
 
 ## Open AARs (2)