Add machine archetypes and amount= expansion

Introduces archetype profiles (windows-workstation, linux-server,
domain-controller, printer, iot-device, etc.) so users get a realistic
service+distro combination without knowing which services to pick.

Adds amount= to INI config (and CLI --archetype) so a single section
can spawn N identical deckies without copy-paste. Per-service subsections
(e.g. [group.ssh]) propagate to all expanded instances automatically.

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

decnet/config.py

@@ -26,6 +26,7 @@ class DeckyConfig(BaseModel):
     base_image: str      # Docker image for the base/IP-holder container
     build_base: str = "debian:bookworm-slim"  # apt-compatible image for service Dockerfiles
     hostname: str
+    archetype: str | None = None  # archetype slug if spawned from an archetype profile
     service_config: dict[str, dict] = {}  # optional per-service persona config
 
     @field_validator("services")