chore(gateway): drop schweitz.internal, default to http://tatlock:8000

The homelab is retiring the *.schweitz.internal domain; in-network
machine-to-machine traffic uses docker container names on the
docker-dataplane network. The deployed tatlock-ui stack already overrides
DESKLOCK_TATLOCK_BASE_URL (Tatlock runs on the host), so only the
fallback default changes.

Docs follow: AGENTS.md M2M guidance now points at container names with
*.schweitz.net reserved for browsers, architecture.md drops the retired
domain (the registry name now matches what CI actually pushes since
c477019), and the README diagram loses the stale hostname.

Co-Authored-By: Claude Fable 5 <noreply@anthropic.com>

docs/architecture.md

@@ -74,7 +74,7 @@ models — the container stays a slim pure-Python image with no CUDA/ML dependen
 2. Buffers inbound PCM until end-of-utterance (client-signalled in phase 1; VAD later).
 3. **STT**: POST to Speaches `/v1/audio/transcriptions`.
 4. **Chat**: POST the transcript to Tatlock `/v1/chat/completions`
-   (`http://tatlock.schweitz.internal:8000`, OpenAI-compatible, **streaming**),
+   (`http://tatlock:8000`, OpenAI-compatible, **streaming**),
    maintaining the conversation history so follow-ups have context.
 5. **TTS**: as Tatlock's token stream completes each sentence, POST it to Speaches
    `/v1/audio/speech` and forward the PCM immediately — see
@@ -335,7 +335,7 @@ Gitea Actions (`.gitea/workflows/build.yml`), following the tatlock/tatlock-ui p
 
 - **Every push to `main`**: lint + tests for the gateway (Python 3.12).
 - **Version tags (`v0.1.0`, …)**: tests, then build `gateway/` into
-  `git.schweitz.internal/jpmschweitzer/desklock-gateway:{latest,tag}`, push to the
+  `git.schweitz.net/jpmschweitzer/desklock-gateway:{latest,tag}`, push to the
   Gitea registry, create a release, and trigger Watchtower to roll the running
   container.
 - Required repo/org secrets: `REGISTRY_USER`, `REGISTRY_PASSWORD`,